The PlayerInteractEvent fires twice when right clicking a block with nothing in your hand.
It also fires twice when a non-block item is in the hand.
The event fires normally (only once) when right clicking a block when holding a block.

I have done testing to ensure the error is not on my end. This has been causing issues for a few of my plugins.

I recall this being a bug a few years back as well so maybe something got reverted when updating to 1.9. Just a thought. Thanks!