Thank you all for your usefull information. I will check it.
Best regards.
tight rollers might be the cause but this is usually accompanied by scraping or some other abnormal noise while the carriage is traveling up and down. michel's suggestion is more common as i've see quite a few valve issues lately. A faulty safety valve can cause this exact symptom.
One trick to see about this is to raise the mast all the way up, then lower it, and see if it does it anymore. If the problem goes away then it is most likely the safety valve. If it does not then i'd look elsewhere. Still you will probably be breaking the cylinders down to see what the problem is.
it can also be a safety valve in the celinders
Could also be caused bij bad rollers (bearings) on the forkboard.
Thank you very much my friend. I will change the seal kits.
Best regards
This could happen when the hydraulic fluid is cold and with no load on the forks. That is normal.
If it happens all of the time and with a load then it would indicate that you need to reseal the smaller 4 cylinders. You should do all 4 at the same time since the kits are way lees expensive than the labor to get to them.