>So, the problem was indeed there. I guess the only change that needs to be done is to add this line to the main program and all will work fine. Of course, I made lots of other little tweaks which my colleagues seem to want to not implement for now.

If you look at that statement, it becomes clear that you and your colleagues don't follow
DRY hard enough. Such a line should *never* be needed to be added in the main program:
It should be in the setup of the class code of the logger. Or at least in the function opening the file.

Also if you had class based logging, any tweak done in the base class would not need to be implemented again ;-)
So that anti-pattern incurred the cost of you trying to find the reason for the perf loss and did not get the benefit
of streamlined routines except for the specific case.

In my code there are a couple of different loggers working - sometimes adding info for
memory state,
tabel size/usage
disk info
stack level,
specififc time incurred (SQL)
time incurred vs. _tally

and other things.

regards

thomas