Cannot connect to a BLE peripheral in nRF Connect Android app

[diode]

The peripheral is actually a dual-mode device, with BLE being a peripheral device.

I can connect to this device and discover the GATT services with the nRF Connect iPhone app and Master Control Panel 3.10.0 Windows application without problems. However, I cannot do it with the nRF Connect Android app (which doesn't even pass through the connection stage). The debug log is:

nRF Connect, 2016-07-29
ABCDevice (xx:xx:xx:xx:xx:xx)
V	12:44:41.583	Connecting to xx:xx:xx:xx:xx:xx...
D	12:44:41.593	gatt = device.connectGatt(autoConnect = false)
D	12:44:46.918	[Broadcast] Action received: android.bluetooth.device.action.ACL_CONNECTED
D	12:44:46.944	[Callback] Connection state changed with status: 133 and new state: DISCONNECTED (0)
E	12:44:46.960	Error 133 (0x85): GATT ERROR
I	12:44:46.969	Disconnected
D	12:44:47.031	[Broadcast] Action received: android.bluetooth.device.action.ACL_DISCONNECTED

This log doesn't seem too informative. It doesn't work on Android version 5.0 and 6.0. Does anyone know what this problem can be?

[diode]

I may have found the cause of the problem. The dual-mode BLE flag data of the peripheral was 0x020102, which didn't indicate the dual-mode property. After setting it to 0x02011A, nRF Connect Android app can connect to the peripheral.