TLDR: An 'Unexpected Error' indicates a connection issue with Open Banking, but your bank statements remain secure. Upload statements as pictures or PDFs to continue sharing without delay.
Source of Funds Error Messages
If you see an ‘Unexpected Error’ message appear on your screen, this likely means there has been a connection problem with the Open Banking technology used in this step. Your bank statements have remained with your bank at this stage, and have not been shared.
Continuing to share your statements
To prevent delay, upload your bank statements as pictures or PDF’s instead. You can read more about this here.