There seems to be many online solutions to this problem indicating that it can be caused by various different scenarios but I thought I would share this hosting environment solution that worked for us thanks to the technical team at OpenHost.
The problem was an intermittent but persistent issue with the loading of files during page render. Intermittent because it could be any random file or files but persistent in the fact that it would always be at lest 6 or so files failing per page load - the exact error being net::ERR_HTTP2_PROTOCOL_ERROR.
We raised a ticket with the tech team at OpenHost and also sent some video evidence to show the issue while we continued to test ourselves and what we did notice is that the problem disappeared when browsing the site using the non-secure http protocol so this is a test you can do to see if your hosting platform is causing issues.
A few days later the team fixed the problem and identified the root cause to be an IIS setting for dynamic IP restrictions which can cause issues when the request limit is triggered.
Hope this helps!