Hi again.
No worries, just trying to help when I have time...
OK, I supose the printers are not the problem, as Epson TM series are probably the best you can find out there.
You can't check if the tables are blocked. Well, You can, but You have to have SQL Profiler or Analiser...but not that important.
Just try to create a new local (StorOps, not HQ). No specific suggestions, just increment the log file size, the timeout interval, re-index, double check the collation (have to be the same as the Local Server and HQ, recommended).
I'm not saying it will solve the problem for sure, but to try somethign different... Do it one day when the store is closed.
Kind regards, A.