All ramparts flicker when a single rampart is destroyed/decays.
-
See this replay:
https://screeps.com/a/#!/history/shard2/W25N13?t=4244395
Thanks to my terrible rampart repairing code I found out that every time 1 rampart decays, all ramparts disappear before being redrawn.
Obviously this is not game breaking but it is rather distracting.