Weird effect of tempo track...

Have a strange issue in 6.0.6

Cue has been recorded, and printed to a mixdown track in the DAW.
Mix is fine, with a continuous program throughout…

On restarting the program next day…there was a dropout in the middle of the take.
There is no visual dropout in the audio file, and if I scrub the file, audio is there as expected.

Thinking it was an automation thing, I first of all switched off all automation…still a dropout.
I then deleted all the automation in the project…file still plays back with a dropout.

So I copied the file further up the Mixdown track…plays back absolutely fine…
Then i noticed that the dropout occurred exactly where I had a tempo ramp entered…
Dropout in and out corresponded to start and end of the tempo ramp…
Switched off the tempo track…and the file played back correctly!!

If I replace the tempo ramp with jumps, file plays fine…
So why would a tempo ramp affect the playback of an audio file?

Possibly CPU overhead during the tempo ramp?

If there are VSTs loaded, did you remove them too? I recall reading something a while back about Kontakt scripts having to do with overloading during tempo ramps.