Well are you doing full copies of production into your test/UAT systems? And are the configurations of all the other databases the same as production?

BTW when you say outside your domain do you also mean outside your network entirely?

Yes, change the join criteria so it's not generating duplicates, but it kind of depends on what's generating the duplicates.  In this case one option might be to change the  t3.c2...

If the question is should you learn the old stuff just because that's what more senior workers had to use, no there is no reason to walk 10 miles uphill...

I also noticed you have this up there -erroraction silentlyContinue , is that by any chance also set for the entire script or is it in a try catch?  All...

Well the best option is to fix the excel sheet so those fields don't show that and either show 0 or just blank if that's what you want.

Otherwise...