Sorry if this is a badly written description, I'm unsure of the terminology for this.

On the touch UI (eg. on an ipad), if you use a tool like a pickaxe or other tool, then start moving around, it often continues to use the tool if it can.

In other words, if I destroy a block with a pickaxe, then start moving around my base, the pickaxe will break anything I get near enough to even though I'm not using it, as if I still had my finger held on the screen.

This makes me a danger around my base – I'm often destroying things at random as I move around.

I'm using the classic UI, and not with split controls. 

This issue first appeared with the 1.4.0 update on the ipad.