Sorry, I am unable to reproduce this. The only way it looks like it can happen is by connecting at 4Hz then changing it to 0.5Hz in the simulator, even then it only drops to searching when the reception quality deteriorates to start missing messages.
The environment plugin does not currently respond to dynamic period changes, the first page 0 message it receives will define the period it uses to follow the broadcast. The next version of plugins will add this capability.