Mac computers dropping off from Aruba wireless networks

I Have a variety of Mac computers in a variety of different locations throughtout the building that are continuously dropping off the Aruba network. this happens even without the user roaming. I have 2 networks.; A company internal, authenticated by AD credentials, and a Guest network with no authentication. The company wlan is the priority. However it appears that throughout the day, the Mac will drop off (without user changing locations) company and connect to the guest network. If I remove the guest network, and connect to the Company, the client will again drop off company ..search and eventually will attempt to reattach to the company network, looking for the credentials. This happens periodically and I am trying to get a handle on it. This doesnot happen on Windows machines. OSX is Maverick and Yosemite 10.10.2. Any ideas? I will admit I am not an Mac expert.

Thanks