Mails are not sent, error: Multipart parser detected a possible unmatched bounda

Hello,
since I added a quiz tag, mails are not sent anymore. The server gives this error:
“Multipart parser detected a possible unmatched boundary”

I have this simple code:

<code>

[text* vorname placeholder “First name”]

[text* nachname placeholder “Last name”]

[email* email placeholder “Email”]

[textarea textarea placeholder “Your message”]

[quiz quiz-290 “The capital of Switzerland? (Spam protection) | Bern”]

[submit “Submit”]

</code>

Does anyone have an idea?

best regards, robert

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