As the title says.

Any further information? What are the events leading up to the link being broken? 

hmm ,,, I'm also exploring the conditions, but I can't find any particular cause ...

When I got on the Cargo Ship it unlink, When transporting items with respawn tactics, the link suddenly breaks and i cant do it.

I moved with a minicopter and the link was broken when I arrived. Anyway it is irregular.

Seems it's to do with moving entities. I'll look when I get a chance.

A little update from me:
Been busy with real life with the holidays and checking up on some of my buddies who got hit by a car in an attack on my local parade and haven't gotten a chance to fully delve into the issue as of yet. 
Over the weekend I'll start a beta branch used for testing new features and this bug fix for you. If you don't mind using untested code.