Note: while iOS 12.1 on iPhone 6 is listed, this also occurs on iOS 11.4.1 on iPhone 5S and likely on Android.

Since a middle 1.6 release (maybe 1.6.3), touch controls have been weird. If I'm using an item by long-pressing outside of the visible controls (e.g. digging with a shovel) and attempt to move afterwards by touching the directional controls on the left, the view will act like I suddenly turned my head in a split-second to some random direction as if the sensitivity was set to beyond the max (e.g. if I'm trying to move left then my view suddenly turns straight up and slightly to the right or something).

I have lowered my touch sensitivity just in case that was it, but no dice.