Steps to reproduce.

Create beacon, activate beacon (I did both jump boost and regen, and haste and regen).

Go to your inventory and left click on a weapon, armor or tool and let it remain as your cursor. It seems that normal items don't cause the issue.

Attachment 1, you will see two issues:
1. There are now corners where the icon is displayed
2. There is an extended black box drawn in the background, that obscures the top left corner of the inventory screen, near where the helmet and chestplate locations are displayed.

Attachment 2, you will see two issues:
1. There are now corners where the icon is displayed, the icon is also mirrored and superimposed over the old (correct) icon.
2. There is an extended black box drawn in the background, that obscures the top left corner of the inventory screen, near where the helmet and chestplate locations are displayed.