Thank you for your guidance - This fixed my issue. 🎉
This was a failed attempt to upload a screenshot showing my docker configuration / presumed irrelevant as problem is now fixed, thanks to you!
This was referenced in an RCON tool I had tried (Probably outdated) called 'ARK Remote Admin' it used a reference in setup pointing to an RCON port and a Query Port. In a desperate attempt to get it working I also tried to forward this port. (Now removed)
Thank you for pointing this out - I have now reverted my port forwards to only use 7777 UDP and 27020 TCP.
Honestly you have been a great help for something I have spent most of my weekend trying to troubleshoot, you had my answer within 17 minutes of my post going live.
Please keep up the excellent work!