We should state that there is a max file upload size of 5MB on Upload pages, and warn users they may still have timeouts with files under that size with lots of rows. This would enable our endusers to understand why a file might not be uploading correctly.

We have a 5MB max file size for CSVs (as per this slack: https://assembledsupport.zendesk.com/agent/tickets/2236)

Other factors can also cause larger file sizes to stall, so it should be best practice to break larger uploads into smaller files to upload without issue.

Error messaging stating that an upload fails because it was too large or timed out while uploading (which could also be due to being too large) would also be helpful.