When disabling revisions for the node bundle to which the h5p field is attached, h5p attempts to update the H5PContent instead of cloning a new one. The update fails since it tries to update the a11y_title field, which doesn't exist on the H5PContent entity. Without the attached patch it isn't possible to update H5PContent.
Disable revisioning for the node entity and try to update the h5p on the field of that node. It will fail with an exception.
Remove the a11y_title field from the h5p metadata.
Review and apply the attached patch.
Active
2.0
Code
This patch worked for me and fixes a WSOD issue. Thank you!