>>>Open to ideas for what this could be.
>>
>>No clue, but why don't you have a converted version along with the original, with some suitable naming convention?
>
>Because users are allowed to make changes to reports and for a while at least, they'll be running both the FPW version (where they'll be able to edit reports) and the VFP version (where only some functionality will be available).

So check the times of the files and re-convert any report where FPW version is newer than VFP. Perhaps in a scheduled job or something. May still be easier than trying to find the cause of this. Who knows what this may be - a revamped version of the floating point bug in some printer drivers or who knows what. There's about three generations of various system components in the background (FPW was published when W3.1 was all the rage). Documentation for most of it was never published. I don't think you'd find anyone who knows someone who'd know where to look.