I need help where we cannot upgrade CiviCRM 5.12.4 to any higher version because of a theme conflict with a paid, premium theme, Benevolent Pro. Details are in CiviCRM 5.17.5 and WordPress 5.2.3 just won't work.

We have logged the problem with Benevolent support. Their initial response is "this is a CiviCRM error." In this case, I believe "error" is the wrong word, but rather there is some kind of conflict, because CiviCRM 5.17.5 works just fine with the stock Wordpress "2019" theme. With the stock "2019" theme, we have also removed any CiviCRM conflicts with any other plugins we use (there was one). Who is to say who is at fault in this case, and how do I diagnose? I'm including a screenshot showing javascript errors on one important contribution page for reference. My main question, though, is to whom do I register this conflict? It seems like discussions on this nice forum are not where I am going to find an answer. I am still pursuing with Benevolent support, but just looking for advice how we can ever upgrade Civi again. Btw, we quite love Benevolent Pro. As a paid, supported theme it is guaranteed to be stable as Wordpress evolution continues, something we had difficulty with a previously customized hard-coded theme that was continuing to paint us into a corner with either Wordpress or our plugin upgrades.

Thanks for any advice here! ***Edit added ~midnight 10/11/2019 *** Adding more details from a local xampp clone of our site. We have 2 instances, all Wordpress data identical and Civi data identical except one is at CiviCRM 5.12.4 and the broken one is at CiviCRM 5.18.2. In both cases, the URL in the address bar is http://{clone_site}.webdev/civicrm/?page=CiviCRM&q=civicrm/event/info&reset=1&id=168

In this screenshot for CiviCRM 5.12.4, note the civicrm source shows http://sdbikecoalition.webdev/civicrm/?page=CiviCRM&q=civicrm%2Fajax%2Fl10n-js%2Fen_US&cid=&r=aMJXH and the event page (event id=168) displays correctly.

In this next screenshot for CiviCRM 5.18.2, note the civicrm source shows http://test.sdcbcdream.webdev/civicrm/?page=CiviCRM&q=civicrm/event/info&reset=1&id=168 and the event page (event id=168) does NOT display.

Note the difference in the Sources in the debug panel is the Ajax injection when it works correctly. Makes no sense to me, but I'm not javascript fluent at all.