I used to work as a programmer in a game company shipping on consoles+PC. The first time we embedded a scripting language in our engine to be used by the level designer's they surprised the whole team with their new found 'toy'. This was great and lessened the burden on programmers.
Fast forward to first milestone (everyone crunching) and the milestone was delayed ... The level designers (not being programmers) had introduced a new category of bugs. Compound that to that fact that this script language had a very very primitive debugger ... hell ...
I didn't imply the scripting engine was to blame. It's unchecked use and the lack of tools for debugging it were mostly to blame ... of course crunching amplified all these problems