Hey @TinoPlusUltra! Welcome to the forums!
Do you think you could get some screenshots or something? Typically Mixamo and UE5 base skeleton do NOT play well together, to the point that there are multiple plugins on the marketplace that will do the work to make it happen.
A star/cross pattern seems strange to me… Maybe the keyframes for those bones? I don’t know, it’s hard to say without being able to see anything.