There is stuff that appears to be disappearing.
Having once done this for a living, first thing to check is your server date which may be up the wall - either incorrect or volatile.
Second thing to check is the overall volumes of data which may be causing corruption problems due to overload in which case you maybe ought to look at archiving some of the old stuff.
It is also possible that some of your code has a date condition based on 'today's date' which is superfluous as letting things run to end is sufficient.
This may not be the cause but it is a good starting point.