Help with strange fault on refrigerated case in convenience store.

[suctionheader]

The other day I attended a call for a multi deck chiller case running at 12 degrees. There were 2 cases each with thermastats/solenoid valves attached to a scroll condensing unit.
The other case was reaching setpoint and cutting out, when that happens the case running at 12 degrees would start pulling down until the other case would cut in.
First thought is that this is a refrigerant problem, after leak testing, pressure testing, vacuuming out and recharging, fault is still there. Liquid line drier has been changed.
Can anybody help ?

[mad fridgie]

Partial blockage (TEV cage filter) or TEV out of calibration