Form Submissions Marked as Spam (False Positives)

I have the weird issue that a lot of legitimate form submissions get marked as spam. Furthermore, in Flamingo the spam log is missing even though I use the latest version 2.3.

According to this article, I should see a spam log entry with the reason why the message was marked as spam:
https://contactform7.com/2019/05/31/why-is-this-message-marked-spam/

However, I only see “Submission result: spam”

I use the ReCaptcha v2 for Contact Form 7 plugin. Aksimet is disabled and there are no disallowed comment keys.

As a workaround I’ve tried to add the following filter in functions.php but it doesn’t seem to help:

// Reduce CF7 Spam threshold to 0.1 to avoid false positives
add_filter( 'wpcf7_recaptcha_threshold',
	function( $threshold ) {
		$threshold = 0.1; // decrease threshold to 0.1
		return $threshold;
	},
	10, 1
);

These are the plugin versions:
Contact Form 7: 5.7.6
Flamingo: 2.3
ReCaptcha v2 for Contact Form 7: 1.4.3

I am at a loss here as I can’t figure out what is marking certain messages as spam. Do you have any idea what else I could check?

Thanks for any hints!