You are losing network connections. POS checks every second to see if there is a network connection. If not there, up pops the error.
Is every device, computers, network switch/router/hub on a battery backup? They must be on the battery side.
Turn off the power saving on the network card. Update the network card driver.
Create a static IP address for the database server machine and point to it in SO Admin | File | Connect and | File | Configuration, then add it to the Client Network Utility | move Named Pipes and TCP/IP to the right | Alias tab | Add | enter the IP address of the Server and select TCP/IP on the left | Add | Named Pipes and the Server's name as a second line.
If using SQL Express, set it to not sleep. SO Admin | Query | New | add the following lines;
-- Turn on advanced options
EXECUTE SP_CONFIGURE 'show advanced options', 1
RECONFIGURE WITH OVERRIDE
-- Set max server memory = 6400MB for an 8g Server machine -- 1/2 for 4g
EXEC sp_configure'max server memory (MB)',6400;
RECONFIGURE WITH OVERRIDE
-- Turn on Ad Hoc Queries
EXECUTE SP_CONFIGURE 'Ad Hoc Distributed Queries', '1'
RECONFIGURE WITH OVERRIDE
-- Turn off advanced options
EXECUTE SP_CONFIGURE 'show advanced options', 0
RECONFIGURE WITH OVERRIDE
-- Turn off AutoClose in Express versions
EXEC sp_dboption 'databasename', 'autoclose', 'FALSE'
RECONFIGURE WITH OVERRIDE
-- Change Recovery Mode to Simple to prevent log file growth
ALTER DATABASE "databasename" SET RECOVERY SIMPLE
Change the databasename to your name in the last two lines and change the memory amount per the "Set max server memory"
