Hydraulic Power Pack - Heating up

Dear Experts
Please refer to attached pdfs of "Hawe Hydraulic Power pack", which is getting frequently heated up although ambience is pretty good ie around 30 degC
This power pack is basically used to lift and lock component during leak test, which is last station and then remains idle
We have taken following actions :

• Replaced oil with new one
• All the valves checked for any jamming etc, spool movement etc found OK
• We plan to replace check valve, which we dont have it now

Can you please advice further
Regards