Thanks for the screenshots. It's not easy to understand why you are having this problem. Could be one of your plugins or theme settings interfering with H5P. I don't think that the problem only arose because you updated to Moodle 4.3. H5P works fine on my Moodle 4.3 sites.
The only weird thing I notice on your Accordion edit screenshot is that the font does not look what it should be. Compare with my screenshot:
