Switching hotbar slots while "using" an item (brushing, eating, shooting) replaces item in new slot with duplicate of item being used.

While brushing suspicious gravel if you switch to another item in your hotbar mid brushing, the item you switch to will be deleted and replaced with another brush with the same durability as the one you were using. 

Steps to Reproduce:

1. Use a brush on suspicious gravel
2. Before the artifact is removed, switch to another item in your hotbar

Observed Results:
The item you switched to will be lost and replaced with another brush identical to the one you were using originally. 

Expected Results:
Brushing should be stopped, the artifact should slowly go back into the sus block, and the item you switched to should remain in hotbar and be seleted.

Notes:
Posted this on the Minecraft Reddit page and people have stated this has happened to them also including on Java edition and with different items.