[russellw]

You are on the right track Vas but it's not a forum based issue as it runs perfectly fine with some browsers - we have been doing a lot of testing to check why it is slow in some.

The issue is with how some browsers handle the TLS implementation. Firefox (from 55.x on, later versions of Chrome and Opera seem to have no issue with TLS 1.2 (the current and more secure version) but IE seems to along with older versions of the above.

Some AV programs also have an impact (Avast for example) because they intercept TLS requests for reasons known only to their developers.

Of course, we can always go back to no SSL implementation but that's hardly preferable. We don't use self signed certs so there should be no caching issues but it might pay to try the following steps:

Firefox
Check for cached certs.
Browse to about:support and then click the Open Folder button for the Profile Folder. Locate cert8.db in your file explorer and rename the file (e.g. “cert8.db.bak”) so that Firefox replaces it. Restart the browser and try visiting an affected site again. If the page loads normally, you have confirmed the issue is related to the local certificate database storing too many certificates with the same name.


Cheers
Russ