I replaced the oil and added 25psi yesterday which cured the slow return at the top, but now it’s soft at the top when I sit on the saddle. Has anyone had this problem and fixed it? If so, how please? Thanks.

Usually caused by having a bit too much air pressure in there.
Its very difficult to find the ‘sweet spot’ for the air pressure where the post actually rises the full amount (without the slow last inch problem), but doesn’t turn into a suspension post like yours is.
Think I just managed it with mine, its only taken me a year! 😆

Cheers, tell me about it. It’s a good post with few moving parts to go wrong but like you say, it needs fine-tuning. What psi do you find works best? Also, it doesn’t help with shock pumps not being accurate below 100psi, both their dial readings and the stroke is tricky to judge at low pressures.