Import field mappings

Have an odd situation, just wondering if anyone else has ever seen this.  We have a solution that's been in use for 10+ years now - so started I think as a v7 database.  Our developers are now running v18 while most clients are v16 or v17.  I made an adjustment to a script last week to an Import Records script step.  It's all internal, just importing a record from one table to another.

In v18 the mappings all look and behave correctly.  However, for any clients on < v18 the mapping of the fields was totally messed up.  Not off by just one field but all over the place.  Same script from the same hosted file showed two very different field mappings in that script step.

I went back in via v16 on my machine - fixed the mappings and now they're OK for all client versions. 

We've got hundreds of scripts in our solutions - never seen anything like this.  Just wondering if it was a total fluke or if it's something we should be concerned about.

Thanks