Audio How can I ensure synchronised play with an external audio track?

I'm working on an art installation that uses ambisonic audio played through Reaper as the audio track for a VR Unity experience (using a HTC Vive and a very hefty, new computer). The player is locked to a linear bezier track which switches speeds at a couple of points during the project, but all of these speed changes are taken into account within the ambisonic track.

Unfortunately, there appears to be some circumstances where the project and the ambisonics seem to become desynced, and the experience sort of falls apart. Does anybody have experience in ensuring that a live vr project and an external soundtrack stay in lockstep?

Happy to provide examples of the project and audio if that would help anyone.

Best regards,

--Rev