@PaulWhite Thanks for that info. However, I don't believe that's impacting this particular issue. In order for the OP's error to occur, a lower-case "i" needs to be returned by SERVERPROPERTY('ServerName') such that it can be upper-cased in two different ways. While I can't test with a hostname containing a lower-case "i", I am testing with a named instance containing a lower-case "i" and can see that SSMS is indeed upper-casing it incorrectly when generating the sp_add_jobserver statement.
@PaulWhite If the OP is using a default instance such that the "server name" is just the hostname, it must be sending a lower-case "i", even if in most scenarios it would be pre-upper-cased according to the character set (as noted in the doc you linked). If SSMS were retrieving a pre-upper-cased "i" that was upper-cased according to non-Turkish rules, then it wouldn't be affected by the UPPER() function in sp_add_jobserver, and the error would not occur.
