Why is my mobile-data (H+) superceding the Wifi by disabling the defined connections ?

[AC Question]

Android ver: 4.2.2
Phone: Motorola Droid M (XT907)

This is very weird. I have tried so many things that I am ready to throw the set at a wall!
Sorry.

So the problem is that when both, the Wifi and the mobile-data is "on" and I come in range where a Wifi is immediately recognized by the phone the mobile-data does not auto-disconnect.
Instead the mobile-data (H+) remains active, even though the Wifi is showing that are recognized routers available for a Wifi connection.
When I try to manually connect to a Wifi router (without switching of the mobile data) it simply shows the Wifi point as "Disabled". There is no IP issued to either.
As soon as I disable the mobile-data the Wifi jumps in without missing a beat and connects flawlessly.
This is also happens when the phone is rebooted and both modes of connectivity are active.

I have tried disabling almost all downloaded apps, uninstalled quite a few, etc etc.

One thing I have noticed is that this behavior is "normalized" immediately after a reboot, or just before when the phone is being shut down.

 

[Rukbat]

This would seem to be a carrier-dependent thing (my phone uses wifi if both are available), but bring the phone into your carrier's repair facility and ask. The phone may be defective, the latest update may have flashed badly - there are a lot of reasons other than "that's the way your carrier has it set up".