Hi, 
I only want to create this post to share my experience and information:

Issue:
When reprinting labels out of the reprint console,
There is no preview shown and if you check the details, the error code 10100 is shown.
If you try to print anyway, you are not able to print and the system shows the error message "Reprinting failed due to unexpected loss of communication with BarTender System Service"
It does not matter, if you try to print from an external computer, or if you try to reprint directly at the database-server. It always looks like, the system is running in a kind of "time-out" situation.

Root-cause:
The logfile of the data base was too big due to a failure in the database maintenance.

Solution:
Step 1:
Increase the size of the log-file in SQL-Management-Studio.
(we trippled the size of the current setting)
Troubleshooting the Transaction log file (.LDF) for the BarTender System Database – BarTender Support Portal (seagullscientific.com)

Step 2:
Run the SQL-query for the manual database maintenance to delete files older than X-days.
Run BarTender System Database Maintenance using SQL Server Stored Procedures – BarTender Support Portal (seagullscientific.com)

Step 3:
Shrink the size of the log-file to your needs, with the SQL-command: "DBCC SHRINKFILE". See bottom of this page:
Troubleshooting the Transaction log file (.LDF) for the BarTender System Database – BarTender Support Portal (seagullscientific.com)

After the logfile had a normal size again, everything worked as fast as usual.

Please consider a server snapshot or data base backup, if needed, before starting any activities.

Best wishes,
Robert