Palm detection when annotating PDF


Hello I have a Note Pro few months old.

I have not used it for a while and today I needed to annotate a PDF.
I don’t know if I am gone crazy or by mistake enabled something, but everytime I rest my palm on the screen to write with the pen, the pdf turn page.

Am I doing something wrong?
I am pretty sure I used to be able to annotate pdf while resting my palm



Could you kindly provide a video to illustrate the problem?