Jetro thanks for all the testing,
I have a TV Finder with the same issue, just tested the battery with 4 cells and the 4th reads 0.009 to 0.050 volts, usually 0.029 volts.
It's beginning to bother me at the moment, just disabled the autolock see what that does.. Looks like a bug, but not sure since it's so random.
It's happening to mine at all voltages. I always get it to switch on again, but even then it's random how long it takes to actually start working..
Hope the problem is found soon..