Drops connections when 2nd user joins (after looking through old posts about this)

Hi all,
I’ve been playing around with this over the last few days and still having a problem where when the 2nd person joins the meeting, both lose their connection. When one gets back it it drops again when the second gets in.

I used the quick install guide and my problem seems most similar to these two that I’ve found:

However nothing I’ve read that has managed to solve my problem.
I’m on a Debian 9 server accessing it via nginx. Java version is 8.

Server is at videoconf dot dunlop dot dev - I’m thinking I might have a hostname wrong somewhere since I accidentally put the TLD instead of the subdomain in when I first installed, then I followed instructions from a post here to fully remove all config and re-install with the right settings.

I’d appreciate any help to get this going and can provide any info required.

TIA,
Sandy