Whatsapp drawing bug / error

Hi everyone,

Since a while I have a bug in Whatsapp while drawing on a picture. When I use any color pencil, and I press anywhere on the screen to make a line or drawing, it automatically draws a line starting from a random angle messing up the picture.

I added screenshots:

1) I selected the pencil, now I want to underline the formula with Vx^2 = Vox^2 +2a etc.....

2) I start underlining from left and and you see the blue line coming from right under the screen before I can continue the line

How do I fix this?

Thank you guys :)

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