i had this problem, is your mousepad colourfull or just 1 colour? mines had different colours and the laser thinks that it has left the mousepad surface and justs jumps to the edge of the screen. you will most likely need to get a single coloured mouse pad. or mayb your reciver isnt able to pickup the mouse properly. it will most likely be one of them. this should fix the problem. it did for me.
hope this helps
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