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At first, I thought this was simply an issue with my code, so I hunted online for a basic doodle-app, and found this page.
It appears that the issue is, at the very least, not my wrongdoing!

Basically, you plop your finger down, and roll it around a bit.
On iOS, this results in a circle being drawn on the screen, whilst on all three of my touchscreen-enabled Android test devices, it instead results only in the initial placement of the finger. The radius of the touch is seemingly blocking Javascript's "touchmove" from registering, until the touch is outside of the initial zone of the touch.
It's only when you do a BIG roll, that the touch registers as movement, and then it happily plays along.

.. This is, obviously, causing problems with my little Foldapuz doodle app.

If you'd like to try the above test on your own devices, be sure to let me know how you get on, and whether this is just a case of me only having cheap-ass Android test devices, or whether it's an Android-wide issue.

Also, if you know of any Javascript/css based ways that I can switch that off, that'll be great.
Thanks!