I’m getting this issue too when adding blocks in the Customizer. “Uncaught TypeError: e.data is undefined” happening within acf-pro-blocks.min.js.
Edit: I didn’t realize how old this thread was. For reference, I’m using 5.9.9. I don’t think I had this issue in the previous version.
OK, so I fixed the issue. In case anyone else runs into the same problem, I had to deactivate the Gutenberg plugin and update WordPress to the 5.8 beta. I was on 5.7 before, but it appears to be working fine with 5.8 (thank god). 😂