If you do find their site works on a other browser (and I mean, the browser, not due to an addon, etc.) then complain to the company / bank / etc.
If they take your complaint seriously then I’d persevere with them… if they don’t then they’re not customer focused and your business (money) goes elsewhere.
Do you have any other hardware between computer & monitor? (Ie a KVM Switch?)
The other post about display ID jogged my memory that KVMs (etc) don’t pass through the data (sometimes?), so just wondering whether there’s another factor here…
Not sure how it would only trigger this on updates, but just building a complete picture of the issue.