oil differential problems

[miz]

hi all i have a grasso rc 46 compressor from 2003 and it is keep falling out on low oil diff but i have plenty of oilpressure and suction pressure is altso ok and discharge temp is altso ok. but it have some cut out every 14 day

i have changed the oil pressure spring and ball with no result

oil pressure is 7.5 bar when running 50-100 % load and 11 bar under startup unloaded so oil differential ia 3-4 bar under load
discharge temperature is 83 degres when running and suction pressure is 3.8 bar
set point on chiller is -6

and controller on this chiller ia a gea gsc simatic C7-633 controller from 2003 like compressor

and compressor is running with Danfoss hvac drive min drive speed is 900 rpm and max is
1350 rpm. and under startup it is running to max rpm and then going down to 900 rpm

hope anyone can help
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