I have seen the same issue.
I purchased a new Solo in the last week, updated to the current software (2.1.1) and experienced the issue described above when using 3DR Solo app (both on iPhone and Android tablet) as well as the Tower App on an Android tablet. The app would connect and disconnect every other second, making it unusuable.
I think it is related to the video portion of the apps. I have an older GoPro (Hero 3) I was trying to use, but eventually just disconnected it.
I found a workaround with Tower (since using the gopro was not my main purpose): go into the settings and tell it to not display the video from the Solo. That made Tower work.