We have a bunch of R750s. Early morning when there are no devices on the network, I'll sit directly under an AP. I'll turn on my laptop (i'm not moving around). My laptop will connect to an AP 40 feet away with two walls between it and me instead of the AP I'm sitting under. I'll move 50 feet in an oposite direction and get directly beneath another AP. I'll be connected to another AP not where I'm sitting despite the fact I'm directly under another AP. I can turn off all the APs but one and then I'll connect to the one I'm under.
As a result of this issue we are all getting much slower internet as it seems almost random which AP we'll connect to. We are on the latest firmware - 18.104.22.168.319