I purchased the XE5300 system at Costco which I believe is bascially a XE75. I tried to use the Deco migration tool, with the intention of replacing my 3 Deco m9+ units (purchased from Costco back in 2018 or 2019) but it wouldn't work with any of the three XE5300s. I hard reset the XE5300 units and then tried to add one to the existing Deco network- that worked. Then tried to make that XE5300 the main unit - no luck. My network isn't over complicated as the Deco's are running in Access Point mode so I just shut down the old M9+ network, erasing them in the process, and started from ground zero with a new network of the XE5300s. After that was up and operational, I attempted to add one of the reset Deco M9+ units to the network to make the network connectivity in my garage better. But the minute an M9+ is added to the XE5300 mesh it won't allow anything to connect and within about 10 minute the entire Wi-Fi mesh crashes. 

And ideas? 

An aside, for whatever reason, the XE5300 units want to daisy-chain their interconnectivity. Main <-> Unit 1 <-> Unit 2 while the satellites are about equal distance from the main unit but Unit 2 keeps connecting to Unit 1 which is a good 50 feet further away with 3 extra walls between them. The old M9+ units always connected: Unit 1 <-> Main <-> Unit 2 like I would expect.

Odd question for cooling - does the XE5300/X75 series draw air from the bottom and passively vent through the top?