So, to identify the cause I tried to execute the above MERGE statement directly and I got the same error:EXEC spMergeTables 'STG.ABCtblXYZ','ABC.tblXYZ'
(0 row(s) affected)
Msg 2754, Level 16, State 1, Procedure spMergeTables, Line 107
Error severity levels greater than 18 can only be specified by members of the sysadmin role, using the WITH LOG option.
This is a case in which an immediate error obscured the actual error.