I have a normal (not dropper) seat post with a quick release. It is running into problems recently. I set it at the right height and not long into a ride after sitting on it it has gone lower.

its really crap because its bad for my knees.

Anyone know why its doing this and how to get it to stay at the set height?

Try cleaning & lubricating the cam on the skewer, if that fails, then buy a better quality clamp.

Is it a Thomson?

Grease the clamp, carbon paste the frame and seatpost.

Is it a Thomson?

That was my first thought 😈

Is the clamp tight? If it is a qr it should leave a mark on your hand. If it doesn’t clamp enough then maybe grease the cam or fit a better clamp. I like salsa clamps.

Try some carbon paste.

Isn’t the real answer, just buy another bike. You don’t need all that hassle in your life.

I bought a double set clamp from bikefridge, which clamps the post to the frame and also clamps to the seatpost to stop it slipping down.