The bug

When opening a GUI, the location the game thinks the cursor is at will not match the actual position of the mouse, the mouse was moved before opening

How to reproduce

1. Move the mouse sideways by a few inches.
2. Press e to open your inventory.
3. Observe that either no item is hovered, or the item that is hovered is not the one under your cursor (if not the case, move the mouse faster before).
4. Move the mouse, and then see that the hovered item resyncs.
5. Close the inventory with esc, and then reopen it with e (do not move the mouse between these steps).
6. Observe that the hovered item is the one under your mouse.

Notes

• The offset seems to be the distance the mouse is moved since the last GUI was closed (acting as if the mouse was moving in a GUI and not being constantly snapped to the center for the camera)
• Another way to reproduce that is to move the mouse about a 3rd of an inch to the left and then press esc, which will cause the "Options" button to be hovered.