Problem has been solved and the most likely root cause was a plugin using lazy loading.
For anyone experiencing H5P content issues as described above:
– Check all your plugins if any of them is using “lazy load”. This was the issue with a plugin in this case.
– When that plugin that use “lazy load” was deactivated, all embeeded H5P content was visible again.
Lazy loading is the delaying of loading/initializing objects, which can cause content buffering issues when rendering of content below the fold.
