A Crash can occur when setting a skeletal mesh's animation instance to None when it has Update Rate Optimizations enabled.
An unverified proposed fix for this is to remove the nullptr check when setting bInvalidCachedCurve within RefreshBoneTransforms.
Enable Update Rate Optimizations on a skeletal mesh with an animation BP
Play
Set the skeletal mesh's anim instance to None
Reproduction is unreliable
FBaseBlendedCurve<FDefaultAllocator>::GetValidElementCount(const TArray<unsigned short,FDefaultAllocator> * InUIDToArrayIndexLUT) Line 385 C++
FBaseBlendedCurve<FDefaultAllocator>::CopyFrom(const FBaseBlendedCurve<FDefaultAllocator> & CurveToCopyFrom) Line 580 C++
USkeletalMeshComponent::RefreshBoneTransforms(FActorComponentTickFunction * TickFunction) Line 2120 C++
USkinnedMeshComponent::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction * ThisTickFunction) Line 796 C++
USkeletalMeshComponent::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction * ThisTickFunction) Line 1247 C++
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-79523 in the post.