[Closed] Suspension Forks Stiffen

Hello I’ve got a Trek 6500 which has got Manitou Axel Elite forks. For some reason the forks work fine initially and compress when I put load on them but after a few minutes of riding they become very stiff and have very little movement. I have completely stripped them down and rebuilt them but still have exactly the same problem. When the bike is left for a while (over night) the forks again are fine for a few minutes then stiffen up. If anyone has any ideas on what could be causing the problem and what I could do to fix it would be much appreciated. Many thanks