I suspected I may get a reply saying version 5 improves upon this.
I will move to FOS 5 at some point, but I can only do so when the release is very mature because I can' t risk other problems. My sites are thousands of miles apart and if an upgrade goes badly, it could mean a lot of downtime and a very expensive fix (last minute flights!). Also my Gen 2 FGT/FWF don' t have as much RAM as newer units, and I worry they won' t handle FOS 5 well. I do see 5.0.6 is cited as lowering memory utilization on the smaller units, which is a positive.
My point though is Fortinet poorly implemented wireless in 4.0MR2, and just when I thought they improved upon it in 4.0MR3, I am struck again with problems. Once bitten, twice shy.