Noisy Chain On Turbo

My Tacx Flux has developed an annoying squeak / whistling noise (difficult to describe) when pedalling in the big ring & particularly in the middle cog of 11/28 cassette. Kind of does it in other gears on the big ring but nowhere near as loud or as often. Doesn't really do it at all in the small ring. There's also a loudish squeak when I'm changing gear.

Gets really quite loud at some point & although the trainer itself works fine it's really irritating.

Googled it & the Flux seems to do a lot of things I can't find anyone describing this issue. Sent a video of it to Tacx & they want me to send it in for inspection but they said they weren't 100% sure it was coming from the trainer itself & I tend to agree as when I stop pedalling the noise goes & the flywheel is still spinning. I'd rather avoid sending it back if I can help it when I need the turbo the most.

The drivetrain was cleaned when I put the bike on the trainer & the cassette is brand new. I've tried cleaning  & relubing the chain again but with the same result so was thinking about either:

Trying a different lube - maybe a wax based lube?
Trying a brand new chain
Changing the cassette for the one I've used on the road (think this is clutching at straws though)

Anyone suffered from a noisty chain on their turbo?

Current solution to the problem is wearing headphones.......