DCar no, other FriendsOfFlarum extensions could also be the cause.
I say that because most extensions, including FoF extensions, are usually tested together with Flarum core extensions during development. But it's a lot more difficult to test all FoF extensions together with realistic production configurations and data so this is rarely done.
Permissions issues are complicated to troubleshoot because the message doesn't say which part of the code or which extension triggered the denial. Even when we know which particular gate ability was designed, there could still be multiple extensions extending the logic for the same ability. Usually the problem is either a different extension denying something unrelated (hypothetical example, an extension requiring the discussion to have a poll, while at the same time private discussions not supporting it) or 2 extensions having priority issues over the same ability (example: tags extension could say something is permitted in a tag, while the extension itself says it's not)
Sometimes the only way to find out for sure is to replicate on a development setup. But for that we need to know which extensions and which settings will allow reproducing the issue, ideally limited to as few extensions as required for the problem to still occur.
