Same Problem was reported by me. From the support was turn of caching and all other plugins and use Theme Storefront on a runnig productive system no sutible idea in my opinion.
By further debugging I found out that all Browser print warning/errors
In firefox 75.0:
Content Security Policy: “‘unsafe-inline’” wird innerhalb von script-src oder style-src ignoriert: nonce-source oder hash-source angegeben
Content Security Policy: Die Einstellungen der Seite haben das Laden einer Ressource auf inline blockiert (“script-src”).
In chrome the following warning is produced:
A cookie associated with a cross-site resource at https://google.com/ was set without the SameSite attribute. A future release of Chrome will only deliver cookies with cross-site requests if they are set with SameSite=None and Secure. You can review cookies in developer tools under Application>Storage>Cookies and see more details at https://www.chromestatus.com/feature/5088147346030592 and https://www.chromestatus.com/feature/5633521622188032.
in Edge
“unsafe-inline” für die Direktive “script-src” in Content-Security-Policy wird ignoriert, weil ein Nonce- oder Hashwert angegeben wurde.
In my opion the IFrame set invalid attributs/cookies and the scripts( mostly the generate new paypal id) stop working.
After some time(>3 hours) a new Id would be automaticaly generatet and all is okey again. Untill the a second user will have an new ID in the time limit.