Forgive me for interrupting your conversation, but I was remembering
something, or infact more than one thing, similar to your
situation:
One is . . . if certain run-time errors fire, they stop a
subroutine from continuing, especially one which had been running
from a "call <such-an-such <subname>"
So, the other day, I tried to run  a sub, and hit a runtime error
on the sub which was called to run from the main sub which I had
been working on at the time, and since it was a "application level"
error, it skipped all the rest of the lines I had written;
thus, it appeared to "randomly skip" some major steps in the code.

The other time, for some reason, which you experts can perhaps
point out, those "ThisWorkbook" subroutines, which referenced code
containing a runtime error, just 'skipped' to the next line in the
code, effectively discontinuing the subroutine which might be
necessary for the process indicated to work. . . . some of those
were when I had put in error traps and other times, if there was an
error trap or a "on error resume next", I was unable to identify it.

Each of those might be part of the problem, I would think . . .
if I'm missing something, please teach me, since I'm certainly
learning as I go . . .