MR60 & MS60 - wirless devices are unable to see one another if both are connected to same ap

My mesh network consists of an MR60 and two MS60.  When two devices are both connected wirelessly to the MR60 they can not see one another, while any device connected to the network by Ethernet, or wirelessly connected to one of the MS60 can see all the wireless devices that are connected to the MR60. (I think the same happens if two devices are connected to the same MS60 but have not verified it, so it may just be when the MR60 is the wireless AP getting used).   For example if a chromcast is connected to the MR60 and I try to cast something to it from a computer, tablet or phone that is also wirelessly connected to the MR60 those devices can not see the chromcast, but if I were to get one of them to connect to one of the MS60 boom it can see the chromcast and cast to it.  Another example, I'm at my desk using a laptop that is connected via ethernet, it can access all devices on my network for file shares, casting, remote access.... disconnect from the dock and go to wireless connection and it connects to the MR60, now it can only access the wired devices and the wireless devices connected to the two  MS60 but can't see or access any of the wireless devices connected to the MR60.  In the following example sketch of a network with wired and wirless devices and an MR60 and two MS60  letters are wireless devices and numbers are wired.  

a, b, c can not interact with one another.  E & F I think can not interact with each other (but haven't checked to see if what happens on the MR also happens on the MS) D can see and interreact with a,b,c,e, and f,  all of them can interact with all the numbers, and all the numbers can interact with all the numbered and lettered devices.   If say C was to go from wireless to wired it could now see and interact with A and B and everything else on the network. Or if it was to got to the first MS60 it could see A & B but prob could no longer see D(again haven't verified if two devices connected to the same MS60 can see one another or not)...

Is there any setting or other fix to get the wireless devices connected to MR60 to see one another? I thought at one time I fixed this, but then it crept back and I've been dealing with it (or maybe I thought I did and the devices just happed to keep connecting to different access points from each other and then started going to the same one  frequently once again) and I can't seem to find a fix now. Baring that, is there any way to make a device always connect to the same access point, it wouldn't fix everything but if I could get the two wireless devices I commonly need to connect to from various other devices to always connect to one of the  MS60, even though the signal will be weaker and bandwidth less, that would solve most issues as I mainly access them from the area where devices are closer to and thus want to connect to the MR60 but those two devices while a bit closer to the MR60 are almost mid way between the MR60 and the first MS60, though there is an extra wall between the MS60 and them.(if I could wire them I would) . thanks for any help you can provide