Two possibilities I can think of.
 
If you have the customer assigned to Print Group B, you do NOT modify the RTM name at printing - Evo adds it for you... Maybe it's trying to print T6SOC4BB.RTM...
 
We don't use Print Groups for Customers but we do for Items/WOs, and on those items that are in a PG, we first get a print cycle with a blank page and then another (including the Print Where dialog) that actually prints. Is it possible that this is what's happening?

The default rtm (or selected rtm) needs to match the rtm for the print group but without the group letter.  For example, if you use group B, and save an rtm called T6SOB4B.RTM.  When you print a packing slip, the rtm selected when asked should be T6SOB4.RTM.  When it prints, it will look for an rtm called T6SOB4B.RTM (in the main DBA folder) for the customer with the rtm group B.  If the rtm exists, it will use that rtm to print.   However, if you choose T6SOB4B.RTM and T6SOB4BB.RTM exists then it will use the BB version.