Pioneer DDJ-Rev7 Instant scratch "drift" issue

I recently picked up one of these controllers and have just started using Instant Scratch to practice some techniques whenever I can't be bothered to get my laptop.

But I've just noticed an issue where the start point of the sample starts to drift away from where I set it. For instance just now;

On the left deck I had sample 4 (the beat pattern) just playing at zero on the pitch. On the right I have sample 2, with my sticker/marker set at 12 o'clock and the deck also at pitch zero. I've been drilling a pretty simple chirp to 1 click flare combo. After about 50-60 seconds I can see that the start of the sample has drifted "forward" so that the sticker has to be about 5 degrees forward to be at the start of the scratch. If i keep going it continues to drift forward.

I then checked the right hand deck and noticed it is doing the same thing but drifting in the other direction. It also takes longer to notice the change more like 90 seconds.

I have power cycled the controller a couple of times. I've tried it with and without something playing on the opposite deck and I've been in to the utility menu and Factory reset each side. The issues persists and appears to be consistently repeatable with the same amount of drift occuring over the same amount of time. The Rev 7 is on the latest firmware (v2.01).

For completeness sake I have checked with a sample loaded in Serato instead and it is functioning as expected. So this appears to be an issue with the Instant Scratch functionality

Is this a known issue and is there a fix? It feels like a calibration issue.