My group has been working on A3S and one of the issues we occasionally run into is that the mechanics occasionally fail due to lag/server ticks. Its not common, but is an annoyance.
There have been multiple instances we ran into where debuffs would fail to swap or the tanks would be unable to pick up tethers despite standing in them. This isn't a case of not being there in time or accidentally swapping debuffs too early, but the mechanic failing to register entirely.