Sonar Artist no playback and zero output level after cutting audio track

Hello,
I recently bought a new laptop (Dell xps 9560 with an SSD disk - no shortage of CPU or RAM or disk space).
Sonar always worked very well on my previous laptop but since installing on the new PC (Windows 10, clean install downloaded from cakewalk) I have a problem with playback.
If I import an audio file into an audio track and play it back it is OK.
If I then cut a part of the audio track then try to play it back there is no sound.  The clock is advancing but the level meter for the track is showing zero output.  After a while (I haven't pinned down what triggers it) I re-try the PLAY button, the tool waits while doing some processing, then it starts to playback.
The settings are all the default settings although I did try various buffer/latency settings but this didn't help and I put back the defaults.
I thought there may be another application running and interfering so I removed Groove Music, but that hasn't helped either.
Does anyone know why, during playback, the level meter for the track could show 0 while the time is advancing (and obviously no mute or volume control issues).
Thanks in advance for any clues.
 
Added later
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Since posting this I've found out that if, after editing the track, I keep hitting "play" then I get no sound.  However, as soon as I re-select the sound card for the track output (realtek, which is already selected) then Sonar is occupied for 10-15 seconds (on a high-end pc with a track of 5 minutes, 24 bit at 44.1kHz), then it starts to playback.
 
This starts to look like a SONAR bug to me.
 
stowyn.