To try to give here a possible graspable solution as well:
Deriving from the intentional aspect and a pattern maybe best visible in
The Sets of Fifteen Area on Uposatha .
There might be the case where a Bhikkhu dwells with careless Bhikkhus, in a careless comunity, but does not recognize them as such, dwells and performes the Uposatha, in such a case there might be no transgression of wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careless Bhikkhus, in a careless community, not proven yet he has doubt, dwells and performes the Uposatha nevertheless without claryfication: in such a case there might be a transgression of wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careless Bhikkhus, in a careless community, not proven yet he has fear, dwells and performes the Uposatha nevertheless without clarifycation: in such a case there might be a transgression of wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careless Bhikkhus, in a careless community, knowingly he dwells and performes the Uposatha nevertheless: in such a case there might be a transgression of strong wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careful Bhikkhus, in a careful community, not proven yet he has doubt, does not dwell and performes the Uposatha with them, without claryfication: in such a case there might be a transgression of wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careful Bhikkhus, in a careful community, not proven yet he has fear, does not dwell and performes the Uposatha with them, without claryfication: in such a case there might be a transgression of wrongdoing, as far as my person may see.
There might be the case where a Bhikkhu dwells with careful Bhikkhus, in a careful community, knowingly, intending torward splitt or out of interest to hide his ways, he does not dwell and performes the Uposatha with them: in such a case there might be a transgression of strong wrongdoing, as far as my person may see.
There is no duty in regard of investigation if there is no reason for one. In cases where doubt or fear arises, seeking clarification is required to be free of mental burdens and free of faults. In cases where one acts clearly (deliberated) against ones knowledge in relation of what is proper, such should be seen as strong wrongdoing. There might be cases where the kammic impact out of current lack of bad conscious, is not assumeable. In those cases it is of cause difficult and depents on possible realisation or trust in supportive other helpers pointing out such. If fully relaying here on them, one might be back to the first case here or the "luckily" perfect one:
There is the case where a Bhikkhu dwells with careful Bhikkhus, in a carefull community, he dwells there without investigations, with no reasons for doubt or fear, and performs the Uposatha with them: in such a case there might be not transgression of wrongdoing, as far as my person may see.
And the perfect, in all aspects, one, the knowingly:
There is the case where a Bhikkhu dwells with careful Bhikkhus, in a carefull community, he dwells there having investigated it, with no reasons for doubt or fear, and performs the Uposatha with them: in such a case there is doubtless no transgression of wrongdoing, as far as my person may see.
If wrong investigated, it runs back to the first case, which has no transgression either.
My person hopes that this quick, merely "self-produced" investigation here might be useful to possible formulate it in more pleasing words and unity.
There perfect case also refects the reason for allowing to prove and investigate for example in cases of precepter or teacher, cases of certain giving into dependency.
It also shows that it is of course not a general duty to "play police and investigator" but not neglect duties in regard of ones progress and also not certain duties to put into maintaining (possible "cleaning") community, -ties as well as far as possible.
At least the Vinaya, as far as known and formost seen, gives ways to dwell alone if such as an equal or better companion is not traced. Here is actually the only reasonable place for dwelling like a rhinoceros for one not an Arahat yet.
Even such as a pure desciple was encouraged to pay honor and respect for the Uposatha (if dwelling with gained Dhamma alone).
That being the reason why it is not so easy as one might have thought, to find ones proper community and it's out of that reason, because there are many careless and many who do not see their duties in certain cases, that it grows more and more difficult when the Bhikkhus turn into "common" sense thought, commonal-individualism and even let them encourage by Bhikkunis or femal tending flows and "leadership" through improper attachment to carelessness...
Now keeping in mind the rule of not doing confession with those of equal offence, one might understand the urgency here as it grows fast, very fast, that possibilities run out and no more Uposatha can be held with real effective effect and in line within very short time.
Since it might fill the grap even better, here a partical citation of a Sutta, yet not given and shared in line of Dhamma rendered in common pleasant form:
‘‘Katamañca , bhikkhave, saṅgāhabalaṃ? Cattārimāni, bhikkhave, saṅgahavatthūni – dānaṃ, peyyavajjaṃ, atthacariyā, samānattatā. Etadaggaṃ, bhikkhave, dānānaṃ yadidaṃ dhammadānaṃ. Etadaggaṃ, bhikkhave, peyyavajjānaṃ yadidaṃ atthikassa ohitasotassa punappunaṃ dhammaṃ deseti. Etadaggaṃ, bhikkhave, atthacariyānaṃ yadidaṃ assaddhaṃ saddhāsampadāya samādapeti niveseti patiṭṭhāpeti, dussīlaṃ sīlasampadāya… pe… macchariṃ cāgasampadāya…pe… duppaññaṃ paññāsampadāya samādapeti niveseti patiṭṭhāpeti. Etadaggaṃ, bhikkhave, samānattatānaṃ yadidaṃ sotāpanno sotāpannassa samānatto, sakadāgāmī sakadāgāmissa samānatto, anāgāmī anāgāmissa samānatto, arahā arahato samānatto. Idaṃ vuccati, bhikkhave, saṅgāhabalaṃ. Imāni kho, bhikkhave, cattāri balāni.
And again here, might all seems nice on the surface, as long as the general tendency of the leader
Sujato Bhikkhu and his ship, and the assembling community around does not turn around 180 degrees, ones does good to avoid this place, not increasing faith in those without and possible weaken faith in those who had gained.
And it's like always mentioned for the benefit of each individual and Saṅghaṃ , since that should be the driving side-effect gift from proper conduct torward Nibbana, instead for the world, for the world. The gift of freedom an a possibility for later generations in that way.
As it might be that one might be not able to leave ones bounds: if serious willing to use D&D, it would be good if installing certain membership restricted forums like suggested here, as a basis work to do, if the frame even allows such effort, since it might be not clear how the environment has be gained... difficult... your work to do and burdens till faith might arise. Just "hints"... may one decide wisely out of which intend and for with aim they are still made.