iPad 4 frequently connects/disconnects from MacBook Pro
After a broad search, I found this solution which worked for me:

On the iPad tap Settings > General > Reset > Reset Location &amp; Privacy. This will reset your location and privacy settings and require you to set up a trust relationship with the PC/laptop again. 

But if you are running out of options ... try that and see if it works. I realize this thread is older, but posting this solution here in case it helps other people.