I am running Core Update 186. I am not seeing any problem as described.
The neverssl.com site is http but the other three are all https and when I tried http they automatically re-directed to https.
The only one that I could not connect to was the api.publicapis.org and that was due to that site not redirecting properly. This was with both http and https. There was a comment that this might be due to my cookie settings but I am not going to change those. I have other sites that do too many redirects and those are also blocked by my Firefox browser.
Just in case could you try to run location update
There has been an issue as per this post onwards.
https://community.ipfire.org/t/squid-was-not-started-at-rpi/11528/2
The squid issue was related to a problem with a specific location database.
I think it is worth just testing with the latest location database just in case that is what is causing your problem.
If that is your problem then you would be seeing messages about it in the
/var/log/squid/cache.log
If there really is nothing in any of the logs for the dropped traffic then the problem might not be with IPFire.
Has your ISP changed something recently.