Just to close this out for anyone doing a search, the issue was inadequate cooling of the condenser. Fan turned out to be OK, but even though the condenser was well vacuumed out, that wasn't sufficient. I had to remove the shroud assembly around the condenser, vacuum, then I sprayed it down on both sides with coil cleaner. What a mess, but it got tons of dirt out. Took a couple of hours.
I did leave the front baffle that sits in front of the two compressors off as it does help cooling and there doesn't seem to be any adverse effect to icemaker operation (was concerned about line freezing) or the drip pan contents evaporating. it is noisier than before, however, but not too objectionable.
My recommendation to any homeowner that inherits one of these and wants to keep it would be to remove the doors, get a handtruck and take the entire carcass outside, and go at the entire top area with compressed air and a pressure washer for the condenser. While that might seem like a lot of work, price a 48" replacement and then it won't seem so bad :wink: