I’m currently running Zwift Play controllers with a Kickr Core to control virtual shifting. It generally works well, but yesterday I was experiencing some odd behavior where a single press of the virtual shifter button would result in upshift or downshift of a random number of ‘gears’, between 1 and 4 typically. Fairly annoying bug.
It was the first time I’ve encountered this. The issue seemed to self-correct after 20 minutes or so.
Shuji at Zwift HQ. Looked through your server logs and your Play controllers are on firmware v1.0.0. Latest version is 1.3.1
Please update using the Zwift Companion app. Here’s how. That should sort you out.
Incidentally - while I was looking at your logs - noticed you still have an ANT+ dongle plugged into your PC. Unless you have something like a heart rate monitor that broadcasts over ANT only - we recommend you retire the ANT dongle. That’s because Virtual Shifting only works if your trainer and controllers pair over Bluetooth. If your trainer pairs to the ANT signal, your controllers won’t be visible in the Pairing screen. Save yourself that headache and put the dongle away.
Incidentally, as of this evening’s ride, left shifts 1 at a time, right shifts double. Assist please 
firmware up to date. KickR 6 wifi connected. TickR bluetooth connection.