OptinConfirm / problem in combination with powermail_cond and missing session

[jensengelmann]

powermail (10.7.0), powermail_cond (10.1.0), TYPO3 11.5.24.

We have configured a form with a mandatory field inside a condition... so if the condition is not met, the field should not be mandatory. We use this form inside a plugin where opt-in is enabled.

When submitting the form, everything is fine. The sender gets an opt-in mail as expected. But when the user clicks on the confirmation link, the problems start: Instead of seeing the "opt-in confirmation" page, the user is sent back to the form with the information that the mandatory field (inside the condition) is empty and therefore the form is not valid. But this only happens if the user does not have a "fe_typo_user" cookie... If the user filled out the form in the same browser, for example, a "fe_typo_user" cookie will be set and the opt-in will work as expected. (But we cannot assume that the user will visit the confirmation link in the same browser he filled out the forms).

Interestingly, the mail object in the backend is activated as expected, but no additional finishers are triggered and the mail is not sent to the receiver.

Did anyone encounter such a problem? Any suggestions on how to solve this?