I did check for that .. and was pretty careful when moving stuff
about. I took the main board out and removed it from it's plastic fame
to give me good access all around

But you still have to factor soldering. If you aren't that great, you will
make mistakes, including some that are only obvious with scrutiny using a
magnifying glass.

Plus, you only soldered big joints. The problem could have been caused by
smaller joints that you may have not paid any attention to. Moving parts
around probably exacerbated the cold joint condition of the existing fault and
might have also created new ones and caused a larger headache. Cold joints can
sometimes be as clear as daylight, but they can also appear just fine to the
naked eye. - Reinhart