Since there are a lot of cheapie dropper posts out now, with sealed hydraulic cartridges, I thought I'd relate some of my experience with maintenance. This applies to various posts like Brand X, Pro Koryak, Tranz X, PNW Bachelor, etc, that have a threaded actuating mechanism on the bottom of the post.

My most recent Brand X Ascend 150mm had developed a little squish, only at the top, maybe 1 cm of give, after less than a year. Not wanting to send it back across the globe for a warranty, and having misplaced the receipt, I dug into it.

I've replaced cartridges before on other posts. You can get replacements fairly cheap online, but with the wide variety of posts out there it's a bit of a gamble finding the right size. A 120mm cartridge doesn't fit a 150mm post, etc. Good luck.

Swapping cartridges and regreasing the mechanism is pretty straightforward, but I learned something important the last time I did this. When reinstalling the threaded bottom of the post, the part with the actuating mechanism, you must depress the slender rod while you thread in the bottom part. Otherwise, you are preloading the cartridge as you screw in the mechanism, and it's made to support your full weight sitting on it, so this is not good. Any rebuild instructions I have found don't address this issue. Am I understanding this correctly, is this not an issue? Please correct me if I'm wrong.

When new I disassembled my post for preventative maintenance, and overlooked this issue. This protocol seems to have fixed it; no more squish at the top. We'll see how long it lasts.