Ahha! I'm going to put my network wizard hat on here and say 'Spanning Tree Recalculation' now.
What (probably) is happening is that some switch somewhere is going 'I think I have a better idea of what's going on than you do, current spanning tree root bridge' and sending out a bunch of STP packets and causing an election, which are causing interfaces to recalculate.
This is normal, and expected, and usually won't cause problems, until you're doing RTP across the link.
Basically, this is one of the edge cases where the default spanning tree config can sometimes cause problems. Normally the best way to fix this is to explicitly deem a reasonably core switch to be the root bridge master, and then put explicit costs on the links, rather than letting them be auto calculated.
tldr: Get your net admin to read this post 