Had one of the early ones. Developed an issue whereby it wouldn’t extend fully. Would sit about 10mm down from full extension unless I pulled up on saddle. Was otherwise fine.
This gradually got worse until it gradually dropped of its own accord, after about 18 months in my possession (bought it 2nd hand).
Had a service with new cartridge & other bits, cost £90 bit as they accidentally scratched the upper & therefore replaced it foc essentially a new post.
First ride out & 2-3mm of ‘clunk’ at top of travel is apparent once more. Thomson say ‘that’s within tolerance’ so I’ll see if it gets worse.
No slop, lateral play or similar ever even when it was dropping on its own. Lovely smooth and light action to the lever and it drops and returns very smoothly and feels ‘nicer’ than the Reverb I borrowed while it was being serviced.
I now use a converted XX shifter instead of the Thomson lever as the cable routing is better and it has a barrel adjuster.
I very much doubt you could do anything inside it, they sent me the old cartridge back after its service. It’s very much like a car boot gas strut, but really high quality, sand standard of finish to all parts as the exterior of the post. No visible way of opening it though.