If you could file a repro that’d be helpful for us to evaluate it.
Note that you do not have to wait for the background task to complete to continue with Burst. If you try and enter play mode or anything like that we’ll stop eager compiling in the background and switch back to the 1.3.X approach (compile as needed). We compile eagerly in 1.4 because we wanted to make the experience when you have Synchronous Compilation on (or CompileSynchronously = true on your jobs) better!