TSECTION.DAT build 42 caused quite a stir, but ultimately it may well have been worth it. Analysis of build 42 positively identified and publicized some tsection-related issues that had been in existence for a while now. The decision was made to roll back the affected clearances on turnouts and track sections that had been stable through build 38, and only carry forward changes made to objects that were new in tsection builds from 38 forward. This seems to be a “best of both worlds” solution, and should eliminate the need at this point for separate US and UK builds.
You should be able to use build 44 with all routes unless there is a very unique need in a route for a specific tsection variation. During the build 42 debate, I set up Train Store to swap out version-appropriate tsection builds depending on the route being selected. I like this method since it means that any route can be paired with the TSECTION.DAT build it was designed with in the first place. This totally eliminates tsection-based errors with signalling, AI’s and paths. I have yet to test with build 44, but when I do, I’ll post my findings.
(Note: Build 43 does not exist, for all practical purposes. It was released, but syntax errors were discovered and it was superseded by Build 44 within a couple of days. There are no routes that will ever need build 43.)