Since you mentioned that a different chain, albeit a supposedly worn Shimano chain, worked and all your other chains were SRAM I would look at getting a different brand of chain such as another Shimano or KMC. I'm aware of Shimano advising against using any of their directional chains for triples and they have never explained why but I suspect it has to do with some of their early directional chains were supposedly prone to cracking and the greater chainline angles of a triple put even more stress on the links but who knows for sure. My neighbor who has a 6700 triple, which came with one of the early directional 6700 chains, rode it until it was worn out and never had a problem but switched to a KMC 10.93 after his shop insisted that he use a $Dura-Ace$ chain. The KMC has been flawless. I usually use KMC's myself and have never been able to tell the difference in shifting compared to any Shimano chain. I wouldn't hesitate to try any of the directional Shimano chains either but would keep an eye out for cracks just in case but I suspect it won't be a problem. Chains aren't too expensive so worth a try.