How to check decimal separator in T-SQL
A T-SQL solution won't help here because SQL Server always uses . as the decimal separator and, as a server application, doesn't honor client regional settings.  One easy way to get the regional setting of the SQL Agent job step account is with a Powershell step with script like:

$numberDecimalSeparator = ((Get-Culture).NumberFormat.NumberDecimalSeparator)
Write-Output "NumberDecimalSeparator is '$numberDecimalSeparator'"


The fact you are having problems with decimal separators suggests the scheduled code is constructing dynamic SQL strings instead of using parameters.  Parameterized queries pass values in native form rather than strings, thus avoiding problems with regional settings that affect date formatting, decimal separators, etc.