From time to time, an Eos Classic may have an encoder screen that registers false touchscreen hits in the corners of the encoder touchscreen (the small touchscreen on the right hand side of the facepanel). This could also be described as the mouse cursor being stuck or jumping to the corner of the screen.
Commonly, the cause is an accumulation of dust and particles. You can sometimes get a piece of paper between the surface of the screen and the facepanel and remove this debris. If this doesn’t work, a qualified service center can remove the touchscreen and more fully clean the assembly.