How do I animate a weapon on my 2D character with a blend tree properly?

I'm trying to use a blend tree to animate my player while holding a sword. I've made animations of my player walking in each direction while holding the sword that I am satisfied with, however when I make a blend tree, the instance where the character is moving "diagonally" causes the sword object to interpolate between the two animations (i.e. the one for left and down, say) and it tilts the sword in a weird direction.

Please see the two gifs attached. In one, my player is only moving in the four cardinal directions and I am satisfied with the animations. In the other, the sword starts to act erratically when the player begins to move diagonally. How do I tell my blend tree to make a decision on which animation to use versus having it try and create fully blended animations on the diagonals? Thank you!

(Links in case the images above are not working:)

https://imgur.com/a/EgpMuHB

https://imgur.com/a/XMiI7HC