Google may have a bug with the URL inspection tool in Google Search Console specific to websites on HTTP/2. The tool shows a malformed response when it is run on the HTTP/2 server.
The individual who posted this on Reddit said “I’m curious if anyone else is seeing this…. When I look at the Crawled Page data in GSC it’s showing the HTTP Response as “Malformed response”. When I run a live test it checks with HTTP/1.1 which is fine.”
Gary Illyes of Google responded “Yeah I’m looking into this. sorry. Meaning to say this is likely a bug in SC.”
Here is a screen shot (click to enlarge):
I asked Gary for an update about this but there was not one to be given:
— Gary 鯨理／경리 Illyes (@methode) February 15, 2021
Forum discussion at Reddit.