On Sunday evening Elli and Nutsinee logged another PSL trip here. Taking trends over this time shows that again the chillers appear to not be bringing down the PSL (first attachment). I've also attached trends over the same time period of all the flow rates: diode and crystal chillers, front end, HPO heads, and power meters. All these flow rates are where they are supposed to be. The third attachment shows all the interlock signals we capture. Only the H1:PSL-IL_OK trips, all other interlock signals indicate no problems.
Rick covered the PSL trip early Sunday morning in alog 18346.
One thing to consider is that the EtherCAT safety terminals go to their nominal safe position, if communication is interrupted. Assuming that the safe state of the terminal corresponds to the tripped state, any communication error between the safety PLC and any of its safety terminals can trigger a PSL shutdown. Maybe check the system for lost frames?