I ran one of these for about 6 months and had a lot of problems with it.
Similar to you, the post seized and quit working after about 3-4 weeks and a few wet rides. Upon disassembly, I found the post had ingested water and mud. After cleaning it, it continued to work for a while longer, but developed an insanely annoying rattling sound from the cartridge rumbling around inside of the stanchion. After spending several weeks thinking my links were falling apart and diagnosing everything else on my bike, I realized it was my seatpost. About 3-4 weeks after that, it seized again.
OneUp support is really really good, but I had this post for 6 months and had to disassemble it 4 times. The cartridge rattle was apparently a manufacturing defect due to a missing plastic piece on the cartridge and they had me wrap it with electrical tape, which solved the problem, but was annoying none the less. Eventually the cartridge failed, but they sent me another one to replace it.
I am glad to see they did away with the o-ring, that thing was annoying and would inevitably fall down the housing and require fishing around in my frame. It doesn't help that Transition, for some reason, doesn't use fully internal routing, so that o-ring could fall all the way to the BB or get tangled up in the silencing kit on the housing on my former bike.
If you ride in dry conditions a lot, you may not have any issues, but we ride in the wet pretty frequently and this post is just not sealed well enough to do so IMO. I like that OneUp is really easy to deal with and their customer support is some of the best I've dealt with, but having to disassemble your post so frequently isn't fun, even if they did make it easy to work on.
Dec. 4, 2019, 6:13 a.m. - Shinook
I ran one of these for about 6 months and had a lot of problems with it. Similar to you, the post seized and quit working after about 3-4 weeks and a few wet rides. Upon disassembly, I found the post had ingested water and mud. After cleaning it, it continued to work for a while longer, but developed an insanely annoying rattling sound from the cartridge rumbling around inside of the stanchion. After spending several weeks thinking my links were falling apart and diagnosing everything else on my bike, I realized it was my seatpost. About 3-4 weeks after that, it seized again. OneUp support is really really good, but I had this post for 6 months and had to disassemble it 4 times. The cartridge rattle was apparently a manufacturing defect due to a missing plastic piece on the cartridge and they had me wrap it with electrical tape, which solved the problem, but was annoying none the less. Eventually the cartridge failed, but they sent me another one to replace it. I am glad to see they did away with the o-ring, that thing was annoying and would inevitably fall down the housing and require fishing around in my frame. It doesn't help that Transition, for some reason, doesn't use fully internal routing, so that o-ring could fall all the way to the BB or get tangled up in the silencing kit on the housing on my former bike. If you ride in dry conditions a lot, you may not have any issues, but we ride in the wet pretty frequently and this post is just not sealed well enough to do so IMO. I like that OneUp is really easy to deal with and their customer support is some of the best I've dealt with, but having to disassemble your post so frequently isn't fun, even if they did make it easy to work on.