I have a client who is experiencing odd results when producing standard reports:
A list of Sales Invoices & Credit notes to screen repeats the same transaction
Running it to file reports correctly.
I have recreated this on their demo data:
To screen:

To file:

They have another report which has the same problem but I don;t have a full list - they are only letting me know when they find them.
They are using Sophos AV but we have checked all the advanced settings so not sure where to go with this as i can't recreate off site.
They also have the issue with Invoices showing incorrect information but being corret on a reprint (although not always).