Erratic response to key input - inconsistent movement. Any help?

[oldladygreybun]

Just got this game, and have played less than an hour. I'm experiencing erratic response to key input for movement (I'm on pc, kb/m, Win10).
For arrow keys, and same also when I tried using WASD instead.

Instead of consistently moving 1 square per key press, it often moves 2 squares per key press.

Any solution or workaround?

I'm aware that the game is quite old by now, and apparently abandonded by devs.
So if there is no help to be had from other players, I'm going to have to refund this as functionally unplayable. *sad*
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Edit: OK, so I've fiddled around a bit more, and realise that there is an integrated 'run' function that moves the jelly block further depending on how long the keypress is.
Ooof I really dislike this. The devs wrote somewhere in an early thread that SHIFT controls 'Run'. But apparantly that changed at some point later then. As I'm not using SHIFT, and dislike the run function which is way too sensitive for my clunky old hands.
Can it be toggled off/disabled somehow?
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Also - 'Resume' doesn't take me back to the specific puzzle or place where I left off, but only to the central hub for that main level. I'm finding it a bit hard to remember where I was, and also tedious to have to go over the same bits of path again and again, for each time I quit out and go back in again.
Is there any way to get back to the actual place where I left off?