I happened to open up the laser's Beckhoff screen this morning and noticed that the flow rate in the power meter circuit was fluctuating between 1.2 lpm and 0.5 lpm. Apparently it's been doing this for a good fraction of the past week. For the time being I've set the trip point to be 0.35 lpm - down from 0.4 lpm. Not certain what the problem is right now. Possibly a partial blockage in an Ophir power meter similar to the problem experienced over a year ago.