Messages coming from XMPP not relayed to Matrix intermittently

[bkil]

Every once in a while, an odd message or two that one types on XMPP is skipped (missing from the chat log on other platforms). The log did not contain any errors around that point in time.

I'm not sure about the exact mechanism, because traffic in our MUC are very low and I restart matterbridge every day.

Not closely related, but similarly touching code parts of XMPP messages not coming in: #1758 #2063 #1552