I also have an issue. It was a brand new 1.14 world, and just the other day I used the kill command (in version 1.14.2) and had 138 golems. I came back just a couple minutes later and saw at least 5 new ones.
When slot 9 is empty, or has anything except an undamaged enchanted pick (or sword), text is gray.
Gray text when hovering over undamaged enchanted pick
White text with undamaged enchanted pick in botton in slot 9.
Adding this here since I didn't see this when I searched...
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!