hy be sure to have the coolant level. inside the filter tank, as high as possible, and the valves as open as possible
thus make sure that flow before the bags is as high as possible
then go through spindle coolant wihtout tool for a few minutes, and look at the tank ... can it keep up ? i don't reffer to main tank, but to that one for thtough spindle, with filters in it
are you actual filters clean ? try to clean them; is the coolant coming into this tank, from the main one, clean ? does it remain like that during a normal production day?it is up to you to find the cause
how thick is the oil level on the main tank ? this to be checked at machine power on, before pumps going on, after the night, so to have the oil time to settle / kindly