Can't drag points on iPad Pro 2021

[skydog23]

I can't drag points in my ganja demos when running them on my iPad Pro 2021. Neither my finger nor the Apple Pencil Gen. 2 pressing on the touch screen appears to be sensed by the ganja runtime. Is this a known issue? Is there a work-around?
Here's an example: the red and the green point control parameters of the app.
https://enki.ws/ganja.js/examples/coffeeshop.html#4tj6k7H3x
THey are draggable on my desktop imac but not on my iPad Pro.

P.S.: I have found a workaround: use an Apple Mouse! I am still curious to find out why interaction with the touch screen doesn't work, but it's not an urgent issue any more.