Service API MapHttpAttributeRoutes conflicts with route registration elsewhere in site

Description

We’re currently trying to implement ‘Episerver.Marketing.Testing’ v2.5.4, however, we’ve run into an issue with the site initializing once the package is installed.

It gives us the following error –

I believe this is due to our config being set as this –

<add key="episerver:serviceapi:maphttpattributeroutes" value="true" />

The error disappears if that is set to false but this setting is something that we need to keep the same though as other functionality is currently relying on it. We have experience the error before when our API routes were conflicting with those of Episerver’s, however, those have been renamed and the routing set to NOT use the HttpAttribute routes. So, I am wondering if it is a limitation of the package that it cannot function without the HttpAttribute routes?

They've tested every suggestion on this thread:
https://world.episerver.com/forum/developer-forum/Developer-to-developer/Thread-Container/2017/4/the-object-has-not-yet-been-initialized--ensure-that-httpconfiguration-ensureinitialized/