Reports randomly "miss" records

Background:

I've made a report that I send to customers. From this report, I've made a summary report that's literally a copy of the first report, but most everything is suppressed except for one section of the original report. Again, from the main report, I've made another report that is basically the summary report, except it outputs all the information in a specific format so I can upload it into my financial system as a flat file. Other than all the suppressed sections there are a few layout changes and such, but nothing that should affect the data, they way it's sorted, etc...

The Problem:

The 3 report's summations don't match up all the time. I'd say they are 90% correct. I did some expanding to find out that the reports randomly drop a record of data here and there. They are terribly small differences too because a record is usually only a matter of cents, however this makes it hell on us because we can't rely on the summary to match what the customer sees which may not match the upload into our financial system.

More bad news:

It appears to be random and it isn't just one report that does it. Sometimes the customer receipt misses a record and the others don't, sometimes the summary misses one and the others don't and sometimes the upload misses. You get the point.

I've gone through the SQL queries that are created and they are literally word for word. They match 100%, even the order of everything (which was to be expected by using a copy of the receipt for the others). Also, at first glance, all the options are the same as well. They pull from the same DBs using the same links. All filtering is in place and all match. Finally, the records read always match up after the reports finish, so they are obviously all pulling the data.

I'm stumped and have been working on this for toooooo long. I think it's time for some fresh minds. Anyone?

Darren