Hi Ede
For the last couple of days it's been raining in North London, and I can't do the gardening. So, I thought I'd try some lateral thinking and problem-solving instead!
It struck me that I could just try getting hold of another audio interface, with the idea that once the Line 6 issue is resolved I could either keep the new interface or sell it on. I was looking on eBay at Focusrite Scarlet units, when it struck me: I already have another interface! It's a Zoom R16 stand-alone multi-track recorder which records directly to SD card...or can be used as a Control Surface or audio interface, via USB.
So, I got that hooked up and it works. I was worried that if I bought another interface I might still have the same problem, and I'd be wasting time and money. Well, the Zoom works fine and there is no trouble getting an audio signal into my computer and into Logic X, and it doesn't break down.
This shows that what we have been experiencing really must be an issue affecting only Line 6 devices.
Once the Line 6 problem has been fixed, I'll probably go back to using the UX2, but for now I have a solution that allows me to make music!
Anyway, I thought I'd let you know :-)
Luigi