Focusrite 6i6 Scarlett interface

My Focusrite interface has developed an issue with the inputs. When I plug anything into either one of the front instrument input's I get an intermittent fault where the input just stops, the activity LED stops registering and I get a weird noise from my monitors. Sometimes it does it sparingly and other times (like in the video below) its pretty much continuous.
This happens whether the device is connected via USB to my computer or not (just monitoring the input). Playback seems to be unaffected, I can still listen to things I've already recorded in my DAW whether or not the fault is present.
I've tried different power supplies and I've tried various different TRS jack leads, it still happens, its definatly not an issue with the jack leads as it does the same with microphones. I've had it for a good few years but it hasn't been used much. Pretty disappointing really. Never had an issue before this,
I'm hoping it's a known issue and someone can advise on a repair. I'm pretty good with a soldering iron so if its a cap or something, I should be easily able to swap it out.
Here is a vid showing the issue, during the recording a bass guitar is plugged in and I'm hitting a string but as you will see, its not picking anything up except for brief moments where the LED activity meter starts to flash as normal with the hitting f the string. You can also hear the weird noise coming from the speakers.

Really hope there's a fix!