Powerpoint strange pen behaviour

[Sheridan]

I'm not sure if this is an issue with PP, WIndows 11 , Viewsonic, Philips or a driver but here goes...

 

In PP - in full screen present mode our teachers write (on a Viewsonic/Philips or Promethean touchscreen) using their finger - this works fine and writing appears smoothly. However if they change the pen colour and start writing again the very first point of contact shows as a dot, then you can see the screen tracing your finger movements but the writing doesn't appear - until you then change the open colour again and then the already written text appears perfectly! Even when the text isn't appearing you can see the screen tracing your movements accurately

 

Its odd - we're on 24H2 Windows 11 and the September release of 365 so pretty much up to date. I have to say I've never seen this behaviour in the past  - so before I start trawling through the hundreds of possibilities (I'm thinking drivers, screen firmware, OS updates, 365 updates and so on) I thought I'd ask the collective mindset on here to see if anyone else had experienced this?