Cannot join slack channels with more than 2 members

[Notmarrco]

Hi,

I'm using dendrite, not synapse, and when I try to join a channel with more than 2 members, I get the error "user is not allowed to change their membership from leave to join".

There is no difference if I'm admin of the workspace or author of the channel.

I opened an issue in dendrite but I'm not sure where this error comes from, hence this issue.

What can I do to help debugging ?
thx

[Notmarrco]

update : if I send at least 2 messages in the slack channel with a regular slack app, then I receive the invite and I can accept it.
For now this workaround is enough for me, but there must be an issue lying somewhere...