Problem with dropouts on my Polar Vantage M

Hi Garmin guys,

I recently bought both Gen3 bike sensors (Speed and Cadence 2). I planned to use them concurrently with both my mobile phone app (Ride With GPS) as well as to my Polar Vantage M watch, since they support dual BLE connections.

Both sensors pair and connect via BLE to both devices fine. Now, when I'm in training and using both devices/apps, speed and cadence on my Polar after a while (riding faster and faster) begins to behave strangely (alternating between real speed and 15.7 kph) and rendering metrics useless. Also cadence graph is totally wrong. 

On RWGPS graphs everything is fine, so I assume it's some Garmin-Polar thing. I haven't still contacted Polar support about this, but plan to.

So, my question is, is this something well known interoperabillty issue or some fw bug? I'd much rather connect both sensors via ANT+, but both Polar or RWGPS don't support it (even though I have ANT+ chip in my phone).

Best regards,