I have been here before with the freezing pi0s. I am running pikrellcam in several pi's with the aim to connect several cameras in network to take wildlife videos but have got stuck with recurring freezez. Typically the webinterface with pikrellcam freezes first, I may be able to log in but not go further, then after a while the pi is no longer reachable by ssh.
The differnt Pi0 have the exact same setup although some freezes, apparantly at random, not at the same time. One pi will work while the other freezes, the next time it is the other way around. One pi will freeze more often another almost never.
I have ruled out power issues and wifi issues, as well as trying smaller resolutions and shorter vids. Sadly when i check system log, messages, etc, I cannot find any error messages. The log just stops around the time of freeze.
The freeze frequently occurs (but not always) when trying to convert the recorded video from H264 to mp4. First I thought that the reason was that the the pi is starting recording or video conversion while trying to perform some cpu heavy system task.
However, @codermike pointed out that setting the memory split (cpu/gpu) to 256 takes almost half of the memory from the cpu on pi0. When I changed the split to 128 i did not get the same amount of problems and the memory usage was completely different, (I also tried the suggestions of @codermike below in the comments and found that I had a crappy Pi on my hands too).
However, I still get some freezes, usually at startup. Could the virtual time setting cause a problem if the video has already started on the real time and when the time suddenly change the pi gets hooked in loop? The freeze happens more frequently when the pi has been off for a couple of days.
Or am I still facing a memory or cpu overload issue? There is a lot of load on the cpu during startup and I am wondering if the pikrellcam starts recording at the same time it may be the cause of the problem.