Same prob, FOUND A FIX - first retarget your desired anims to another normal UE4 skeleton, like any one that you’ve already used for retargeting. Then, retarget to your desired skeleton from that one. ie., i was crashing with Sword and Shield AnimsetPro going to my mixamo char. So, i retargeted the Sword and Shields to a Mage Anim pack skeleton I had already successfully retargeted from. I put those anims in a temp folder, and then I went back to my (already setup and working) mage IK Retargter and simply exported the anims I wanted - no crashes, no distortions. GL y’all!