Hi Rob,
Your sensible explanations are once again helping keep me sane!
I have tried using the -continue option as you suggested. This appears to get around the msg=MultiBandGroups: Unable to open file error but still returns UnicodeDecodeError: ‘utf8’ codec can’t decode byte 0x9e in position 1: invalid start byte
Therefore, I think adding the full path to the slspec.txt file for the --slspec flag might have worked, however the file “my_slspec.txt” or “myslspec.txt” is failing to be read regardless.
From reviewing Hamed’s recent post and the corresponding GitHub issue a solution did not jump out at me. Did I miss something?
It seems like the update for this should hopefully be available soon (days not weeks) 
so I’m thinking my best option may be to wait it out. Although, this may not solve the unicode issue…