Subtitle Edit text to speech creates variable speed audio

[timo1735]

Just got back to using the latest version of Subtitle Edit this week after a few years absent to use the translate audio
capability to create an English language track to get a text to speech synth voice.
Tried this video https://www.youtube.com/watch?v=9RUf0EVWkZc
and got the audio to subtitle done and had Subtitle Edit create a new video
with the new voice track. The audio track it created has audio that speeds up and
then comes down to normal speed. Anyone know how to prevent this??
I've attached a short portion of the audio so you can hear it.

Timo1735