You'll want to consult your financial institution to know the limit. QuickBooks only have account name character limit. You can find the character field limits at the link below.
I'll also share with you our page about fixing bank upload errors that I'm sure you'll find helpful. It contains temporary and easy to fix resolution to manual-upload related issues.
Please know that we're always here if you have other questions or concerns, so don't hesitate to swing by anytime. Thanks for posting and I wish you have a good one.