Polar 115 ED clamp issue

Hi i have a problem with the clamp of Polar 115 ed. When the clamp goes up, it bounces at the end of journey. If i release a foot pedal slowly, there is no bounce. I changed 2 valve y27 and y27a to y33 and y33a, there was also no bounce. So is it due to fllow returning to tank too fast? Any suggestions for Solve this problem? And can i adjust the pressure reducing valve?
Thanks

 

Hi sir:
Measure +42Vdc is there in the valve, and there are in tolerance 5%
Bleeding the system and replace the hydraulic Oil, and put enough until the Plastic visor is Full.