Hello Footman,
I’ve attempted reproducing your case but haven’t had much luck. I’ll try to be as detailed as possible so that we can try to figure out what the difference is that is making us see different results.
I created my project based off the C++ version of the Third Person Template. I then added a class based off Actor from the C++ Class Wizard and called it WeaponActor. I set this up using your code and then used the code you provided for the character inside of the Third Person Character. I’ll attach the entire source for the project here.
The way I set it up, it spawns the default 1M_Cube from the ThirdPersonTemplate on the index_03_r bone of the Mannequin skeletal mesh that is assigned to the ThirdPersonCharacter. I then opened the Sequence Recorder window, hit “New”, began PIE, selected my ThirdPersonCharacter actor in the scene from the dropdown beside “Actor to Record” and then hit Record. After that I ran around for a bit, alt-tabbed back to the Sequence Recorder and hit Stop before stopping PIE itself.
Upon playing back the sequence that was created, the cube appeared to stay attached in the correct spot and follow the animations correctly.
Could you give my method a try and see what results you get? This was all tested in 4.12 Preview 4 as well.