I've found the problem. I changed the injection in the header for Cookiebot from:

<script id="Cookiebot" src="https://consent.cookiebot.com/uc.js" data-cbid="00000000-0000-0000-0000-000000000000" type="text/javascript" async></script> 

to

<script id="Cookiebot" src="https://consent.cookiebot.com/uc.js" data-cbid="00000000-0000-0000-0000-000000000000" type="text/javascript" data-blockingmode="auto"></script>

The new data-blocking-mode="auto" is now necessary for Cookiebot (not anymore 'async').

If I changed back to 'async' ReCaptcha is OK.

Now I need a solution to use the data-blockingode="auto" because of GDPR.

"Cookies will now be blocked prior to consent and controlled automatically based on what the website user has consented to. "