Skeletal mesh merge issues - has anyone figured it out?

I am not a C++ programmer, so I am not 100% sure what’s going on here, but after successfully following Epic’s docs about modular characters in UE4:

I ran into the following issue - it seems that all sockets are stripped after the merge in the shipping build (or any standalone build for that matter).

While in PIE, everything works as expected. When running shipping build on Android, everything that should be attached to various sockets is at character’s feet (where it’s placed by default in the Editor).

Any idea why ? Has anyone found a fix ? Thanks