>Your script is not protected against invalid table names. You should use QUOTENAME() function
>

>Select 'ALTER TABLE '+ QUOTENAME(tab.name) + ' DROP CONSTRAINT '+sysobjects.name
>

You are correct. I usually put every table name between [] in script in case this is a reserved name. It is still a mystery that this is working as is on two servers but not on the production one where the three of them have the identical database, with the same OS version.

I will make the adjustment and next week, I will be able to confirm if this has resolved the issue.