Hello Ben,
QuickBooks Online accumulates cache on your browser. It's possible that the cache storage is almost or already full. Thus, slowing-down QuickBooks' performance.
We can do browser troubleshooting steps to get rid of any cache-related issues.
- Use a private browser and do the bank transfer process.
- If the performance speeds up, you can clear the cache storage of your regular browser.
- Otherwise, use other supported browsers.
If the same problem occurs, I'd recommend contacting our QuickBooks Customer Care Team. They'll be able to further investigate this. Here's how you can reach them:
- Go to this link: https://help.quickbooks.intuit.com/en_US/contact.
- Select QuickBooks Online United States in the upper-right corner of the page.
- Go to the first section and choose Running your business in QuickBooks > Banking.
- Go to the second section and choose how you want to reach them (phone or chat).
Let me know if you need anything else.