SM430 interoperability mode not working in 13.4 ?

We are having several reports that SM430 with firmware 13.4 are not switching automatically to interoperability mode when having configured both modes.

The AP450 it should connect is running 13.1.3 and SM 13.4.

We believe we reproduced your setup in our lab with an PMP450 AP running 13.1.3 and 2 - PMP430 SM's running 13.4. and Auto Interoperability worked.  We had them registered in PMP450 mode, selected the "Switch Radio Mode and Reboot".  The SM came up in PMP430 mode and after about 5 minutes the SM changed to PMP450 mode and reregistered. 

How long are you waiting for it to switch between modes?   The scanning for operational mode between 430 and 450 interop runs for 10 minutes in each mode before swapping modes.  The SM must reboot between scanning modes..  

Also, the SM will start with the last mode it was attempting when it reboots and the 10 minute timer will start over.   If the SM registers to a 430 or a 450, that mode is what will be used on the next scan.    I.e. if it is registered to a 450, and it reboots or loses registartion, the next scan will start in 450 interop mode rather than starting over with 430 mode.