Need help with Daikin EWWD-H-GX chiller

Hi,
Need an advice on Daikin EWWD-H (same as McQuay PFS C) chiller. 2 compressors, one circuit.
The issue is the oil return, compressor 1 become lack of oil in the separator. I think this corresponds to running on low load (~20-25% in night time, weekend).

Both load and water flows seems to be OK. Both approaches, discharge superheat also OK.

Primarily the compressor 1 was running dry on oil. Then daikin guys came and changed oil filter on the 1 compressor (compressor 2 oil filter was changed by them previously). Then they started chiller and it worked OK. As soon as they left compressor 1 became dry again. Another oil vessel became filled higher then upper sight glass. Then I came and found these shutoff valves https://prnt.sc/ggzcct closed and opened it. (Legend http://prntscr.com/ggzhws)

The chiller become to run well for more than a week including 2 weekends.
The oil level was:

• mid of bottom sight glass while running
• top of the bottom glass while stopped.

But today the oil level descended below bottom sight glass again.

Questions:

What is the logic of oil control: when solenoids 18 http://prntscr.com/ggzjvo corresponding to each oil tank have to be opened?

All 3 oil delivery paths seems to be OK (main supply from the oil tank, draw back from flooded evap and equalizing tube). What should I check to solve an oil issue?

Is there a possibility oil level in the vessel to be raised while corresponding compressor is stopped?

I found no setting (neither in highest level menu nor in the manual) for low delta p alarm across
the oil filter (line) so compressor can proceed running without an oil. Is there a way to set this value?

Is there some sort of ready to go monitoring software for siemens based microtech III control to log parameter trends for duration of some days?