RouterOS on RB751U-2HnD Quickset lost device

Hi,
I have already used a lot of this devices in default quick set Home AP mode.
Today I need one rb751U-2HnD in cpe or PTP Bridge mode.
I have clicked (both webfig and winbox) on Quick Set combo box in top right of the quick set tab.
As i confirm the alert, i lost connection to che device (no more ping also)
With winbox i can search for the device, it find the device with the right mac address but without ip address (0.0.0.0). If i try to connect it can’t anymore.
Sometimes, winbox crash if i try to change the quick set mode.
The only mode to recover is to use reset button.

Anyone has this problem?
How i can connect to the device after the quick set mode change?

Thank You

Francesco Usseglio