Thanks for the video post. I can see somethings going on that I can look into.
Can you post a screen shot of the BP you have setup for your character/projectile along with the destructible mesh properties you’ve set for your Box and for the Projectile Ball.
When you post the screen shot of the Destructible Mesh properties it’s probably easiest to select the eye in the top right next to the search bar. Select the option “Show only Modified properties” this will condense the image to keep from having a larger image (unless you’ve tweaked a number of settings across them all ).
I am slightly embarrassed to say that I solved this on my own, I didn’t realize that a parent mesh had a sphere also doing collision. It just so happened that they were trading off (depending on angle) who actually was getting the ‘onHit’ call first.