Webhelp search works in IE11 from un-upgraded RH2017 but not from RH2017 Update 2

I have RH 2017 and generate webhelp. In recent webhelp builds, the Search function wouldn’t work in IE11 when the help was accessed through the application from a Unix server. No search results. The Search function works fine with Chrome and Edge via the application from the same server. If I view the webhelp from the hard drive on my laptop (i.e., locally), it also works fine.

I tried changing settings, changing the skin, rebuilding, re-posting, testing etc. The search function had run without any problem in the Webhelp I generated back in August, but not now.

Then I saw this post ("Robohelp 2019 & Internet Explorer 11 issue"): https:://forums.adobe.com/message/9702368

So I unchecked the “Display intranet sites in Compatibility View” option in IE11 and the search function worked in IE11. But I wondered why search worked in the August webhelp regardless of the setting and stopped working in webhelp buids in October. Then I remembered that I updated the RH 2017 install on my laptop in August to Update 2 (13.0.2.334).

So I copied my RH 2017 project to a laptop with the original, un-upgraded RH 2017, and generated webhelp, and I bet you can guess what happened -- the Search function worked in IE11 regardless of the “Display intranet sites in Compatibility View” option.

So I will be building webhelp on this other laptop with un-upgraded RH 2017 from now on. It's very annoying (since it is a different person's laptop), but at least I don't have to ask users to uncheck the IE option. Does anyone know of a resolution for this other than restoring the un-upgraded RH 2017?

BTW, I did make the fix described in "Cannot collapse the ToC of Webhelp output in Google Chrome" to whthost.js, but that did not help.