I have come to the conclusion that it is completely random, automated cache emptying may be a problem. I think others have encountered this issue with version 2.3.x.
Varnish is not installed yet. I tried it before, but I couldn’t get it to work. I think it would be nice to speed up a lot.
I saw some M2 pages where a compressed JS file was downloaded by the browser. These were not 2MB, only 200-400KB.
I am currently using http2 protocol and did not merge the js files due to the large size. So it take it in pieces, but 256 requests, which is a lot.
Do you have a tutorial video showing what modules should be turned off for fewer JS hits, or doing advanced optimalization? This is a very interesting topic for me.
btw, sorry for my english