I guess the @ notification didn't work here.
For passers-by, I'm pretty sure this problem had been caused by a missing file. I had several screwups with the scripts I used for generating the packages. Hopefully that's been fixed. Much of the confusion stems from imblend() suppressing the complete error message backtrace. That much has been improved.
The suspicion that this might possibly be an issue which manifests only in newer MATLAB versions appears to be false. I've since successfully tested the given code sample in the forum editor (R2022b), both with and without IPT passthrough enabled. I used peppers.png, but I don't believe the problem had anything to do with the image itself.
