I need help with my Audio Interface issue

This is a long post as I go quite in depth about my findings to help anyone try help me find some solutions so I apologies in advance.

I usually use a pod go wireless to play guitar so I have never encountered this issue before I had it get put in the shop for repairs. So I cannot confirm if it’s a new issue or one that was always there.

Recently I’ve been playing guitar through Logic Pro using my Behringer U-Phoria UMC404HD, usually using a guitar amp sim just until I get my pod back, I’ve noticed and issue when I have my headphones plugged in if it’s too loud it will feed back into my input no matter which one is selected, I played around and read some forums and stuff but to no avail, i have narrowed it down to debunk a few common theories

it is not my guitar pick ups, even when the guitar is fully unplugged and my gain is turned down on the interface it still feeds back.

When I turn down the headphones fully and turn up the actual output which would be through my monitors there is no feedback meaning it is solely the headphone port.

I do have the knob turned fully to PB meaning there is actually no signal from my input being monitored so it should only be the computer audio

Another thing I’ve tested was getting a random kick drum sample on YouTube and seeing if it was something to do with logic itself and the issue continued meaning it’s not logic itself and is most likely an external issue

These are all my findings so far and I am completely stumped, I assume it’s something to do with my interface but I don’t know what it could be. I am on the latest version on Logic Pro and my Mac does need an update but away from that I’m unsure if it will fix the issue as it is the version before the recent update I am on

Please let me know what else I can do and if it can be fixed or is it doomed, either way it’s not the end of the world I do get my pod back soon but I would rather fix it as I do record vocalists and I don’t want this to effect that in the future.

Any help will be greatly appreciated.

Edit: also if I have the headphone output turned up but the headphones aren’t connected there is no feedback, it’s only when I have something connected to it