As a forewarning, I didn't make the animations, my contractor did. I don't have spline, he doesn't have Unity.
Now. I have two animations from him. One of the animations a shield sprite that's attached to an arm goes from hidden to unhidden to hidden. There's a second animation that doesn't involve the shield, so it's hidden throughout.
First issue, when the animation involving the shield is played, the first time the shield remains hidden throughout the animation. Once it's played a second time, it works just fine.
Second issue, when the animation without the shield is played after the animation involving the shield, the shield is not hidden. According to him everything works looks fine in Spline.
The exported files are attached.
There is also an "idle" animation which is supposed to be just a single frame animation, but when tested in Unity it just freezes whatever current animation frame it's in.
Basically no single animation works as expected.