Frontend JS Error e.getAttribute(...) is null

[dennismetz]

In the current version (12.3.5) there is a JS bug which prevents the sending of forms.
Uncaught TypeError: e.getAttribute(...) is null

The error has probably occurred before, but has not yet led to the form not being able to be sent at all.
It is a normal form with a few fields, no multistep.

TYPO3 12.4.19
Powermail 12.3.5-12.3.2 (probably also previous versions)