Tacx emailed me back and said to use the utility app to update to version .19, but that isn’t released on the iOS app yet.
" John - Tacx Support Team (Tacx)
Jan 25, 08:47 CET
Dear,
We’re sorry to hear that.
We advise you to download the latest firmware version (0.19) via the Tacx Utility app.
This should solve the RPM drops’s.
Kind Regards
Tacx Support"