On one of our customer systems, opening an H5P Dialog Card activity results in a blank page. The following error is shown in the developer console:
"Unable to find constructor for: H5P.DialogCards 1.8"
I can't reproduce this on other systems, but I also don't know what else to try than clearing the cache. Deleting and reinstalling the content types isn't an option as that would mean losing all the corresponding contents on the system, if I understand correctly.