You could affect the object itself, if it detects an object inside it’s bounds it would teleport or push it outside. If there’s just a few specific objects that have this problem it’d be a good strategy, i think maybe also enabling CCD on both the player and the object might prevent this issue from occurring at all, but it could prove expensive if it’s a lot of objects.
Your sphere trick is cool but a bit limiting in the sense that it could trigger when certain projectiles strike the player and it also wouldn’t detect if a part of the player is stuck inside an object that is outside of the sphere.
A similar approach to your sphere trick would be to do a line-trace from the pelvis to the foot or ground, and if the trace hits something between the pelvis and the foot then it is a fairly safe bet the player is stuck inside something.
Depending on how you implement it, it could be cheaper and more effective than the sphere collider trick (by itself a single line trace from the pelvis to the ground would be about as effective as the sphere collider, however you can easily add more traces, one from the left side of the pelvis down to the left foot, right side of the pelvis down to the right foot, and you can also send another trace up from the pelvis to the shoulders as well to cover a wider area)
if more than one trace fires off it’s a safe bet your actor is inside of something, and if one trace fires off for a longer time than 1 second it’s a safe bet your character is partially stuck inside of something.