Chain skips only in one gear

Sounds like the bearings. They are cheap and easy to swap.

Solved it last month with a new cable. Night and day.

Make sure the wheel is seated fully in the dropouts.

Marking this one to follow, same issue here.

Check the simple things first: tension, limit screws, and that everything is tight.

Had exactly this. It turned out to be the cheapest part in the whole system.

Bring it on Thursday and we will have a look together.