WAX 615 Wifi Instability

I have had no issues with either 610's or the 620's in operation, configuration via insight across about 20 site installs, and managing/monitoring these sites and AP's remotely for 3 to 5 years.

I am just getting ready to roll out about 6 of the 615's. 

Why change from the 610?

Better performance of the 615 (as per specifications) 

Why a change from the obvious more robust 620's?

Cost.... and at +/- $229 for the 620, over the $129 +/- cost of the 615 and very close cost similarity of the 620 to the 615... well...

The cost to benefit ratios with added throughput and higher device counts was one reason for moving from the 610 to the 615 ....

Im wondering if this roll out will lead me down a dark path with spotty issues like this during the life of the product. 

I'm now a bit concerned over the durability of these units. The open design of the 615's where there is actually a visual to the pc Boards and components through the back (see photos - whereas the 610/620 units are pretty much sealed units, dissipating heat through the metal housing or heat sink on the back of the units) could provide for better cooling of the 615 at the cost of some durability of foreign material impacting the boards under the "thin skin" of the 615.

Since the 615 units will be mounted with the air vents up, the heat dissipation should work well... with little prevent the heat escape. (mounted to a 2x4 joist and minimal restriction).

Any thoughts?