Wierd scenes inside the hydraulic tank

I am experiencing something I have not seen in my 25+ years working on equipment. the hydraulic oil level is being drawn down out of the sight glass with the engine running and machine not operating. Oil level is will return slowly to proper level when machine shut down. Machine is a 2006 Terex TXC175LC-1 which is actually a Daewoo Solar 175, now owned by Doosan. It has a Rexroth Uchida Pump with a Doosan engine and Doosan main control valve. The Hydraulic return filter has been replaced and suction screen checked and cleaned. The hydraulic oil was recently replaced due to water contamination and system filtered to remove any remaining moisture. The oil level did not exhibit this problem when system filtered. I am also experiencing a low power condition due to low main relief pressure. Other trouble shooting has led me to a main relief that will not adjust. Pressure is 200 bar and should be 310. I believe the oil intake restriction is the cause but I will be replacing the relief later today. Any thoughts or ideas are appreciated!

Wierd scenes inside the hydraulic tank