This happens to me pretty often also but not so much of an issue when I am using return/teleport function but rather when many others around me are. It pretty much always happens when those trains of RMT Lalafells teleport away from the Adventure's Guild in-sync while I am nearby. My screen feels like it nearly freezes for a full second at times when this occurs.

At no other times do I have any frame rate issues while playing at my current settings.
My guess would be that showing multiple teleport animations at the same time can be very intensive on the computer to show. It feels like it just lags when those lalafell teleport away so I always find myself running away from them if I can. >_<