[Closed] Gears skipping in middle ring advice

I've replaced the chain, cassette and gear cables on my bike. First ride last night with the updated drivetrain. In the granny and big rings the gears shift no problem.

However in the middle ring the gears are slipping on the cassette. On the flat they change ok. Once I start putting any real power through them or start cycling upwards the gears attempt to phantom shift and there is a lot of crunching noises coming from the rear of the drivetrain.

Any ideas on fixing the issue as it's not something I could replicate on a workstand as it's only happening with some power being applied.The shifting on the front is ok, the chain doesn't seem to have any obvious issues there.

Cheers!