Text file losing data after append

We have a system at Walgreens cor****ate HQ that allows users to create
simple forms to be used on the web.
We have found over the past 2 weeks the some of the records (about 5)
append to text files are not appending to the end of the last record
entered rather append over the last or next to last record with the
new record.  It is not a timing issue since the appends occur hours
apart.

This system is designed in java known around here as "QuickForms".

Any Ideas?