Hello John
I’ve disabled all plugins and step by step enabled them again. The “bad” plugin is “Advanced Custom Fields: Contact Form 7” by Taylor Mitchell-St.Joseph.
This is causing the issue.
While the developer does not provide a fix, I found a solution:
https://github.com/robertark/acf-cf7/commit/1e9916e259664877d107b10b48c2efb3c46b9894