Mining with a damaged mending pick can sometimes be interrupted by picking up experience orbs, causing the mining to restart.

The only item with mending is the pick I am using to mine. A video of the issue can be found at https://youtu.be/P3kuJOVuWIk

The issue occurs a couple times, but the most obvious are at 0:23, and the iron block at 0:29.

Let me know if you need to know any other details.

Thanks!