We had some trouble getting re-locked this last time. 

Several of the locklosses that we had while trying to get back online were due to MC2 M2 saturations, much like we saw in early September.  See, for example, aLog 21169.  It looks like this stopped being something that we were noticing, so we didn't put too much effort into determining the cause. Anyhow, we were able to lock, and are currently back in Observing mode, so maybe we should just sit tight and see if this happens again, or if it goes away again.