From time to time we see some big glitches when DRMI is locking, and it seems likely that some of the time these things cause locklossess.  We sometimes wonder if this is a problem with a glitchy osem, especially when we are having difficulty locking.  

Here is an example of this happening, DRMI survives.  In this case at least it was the BS oplev glitching, as you can see the sum drops at the same time that there are drops in the DRMI build ups.