Are you also finding incorrect fields in the header (wrong CustID, InvoiceNum, etc.), or is it just the page numbers that are messed up?
Batch printing SSRS forms has been something many of us have struggled with for years… You might find some insight from this post: SSRS report randomly displays incorrect PONum and blank OrderDate - Kinetic 2021 - Epicor User Help Forum (epiusers.help)