My TranzX post (LIKE THIS), probably 18 months old, has stopped working properly.

I’ve stripped it down as far as I can and there’s nothing wrong in the outer tube or seals etc. The issue seems to be with the actuator pin in the head, which the remote cable/lever operate. It’s seized/not being worked properly, so the post won’t lock out. I can manipulate it manually, it will move, and I’ve left some lube to soak into it, three days on, no better.

Any thoughts?