MLT-BT05 bonding problem

Hi
I'm trying to build a system remotely controlled by a smartphone. For communication I've chosen Bluetooth. So I have a module MLT-BT05 and have it successfully connected with Arduino Uno. I can issue AT commands and there are no problems at that side.

In Bluetooth communication though it's not that good.
If I connect to the device using standard Android BT management I can see the device but can't pair with it:

If I use nrfConnect application I can connect to the device but can't bond to it:

When I use Serial Bluetooth Terminal application I can connect to the device and can send and receive data via this one.

So the problem is mainly with pairing (or bonding in BLE terms)
I tried to change the authentication type so the PIN is required always (AT+TYPE2). Then I can't connect to the device by any means. I always get message that PIN is incorrect although I made sure the PIN is 123456:

AT+PASS123456
> OK
AT+RESET
> OK

Also I tried to change role of the device from slave to master (AT+ROLE1). In this case all application showed "gatt status 133". I'm not sure master role is ever supposed to be used to I just changed it back to slave (AT+ROLE0).

Did I miss anything else (I have very little experience with Bluetooth) or it's just faulty device? I know MLT-BT05 is a clone of a clone so I don't expect high production quality.

ralfeus:
I can issue AT commands and there are no problems at that side.

When I use Serial Bluetooth Terminal application I can connect to the device and can send and receive data via this one.

Did I miss anything else or it's just faulty device?

It would seem that the device is 110% kosher, and the same can be said for your wiring. The real problem is working out what your problem is.

The MLT-BT05 is just a version of the HM10. I think it is just a brand and no different from any other HM-10. I understand BLE devices need to have specific BLE apps on Android. If you can send and receive data, I guess you have the right app for the job. Similarly, BLE needs to be in the correct mode to work as terminal device, which you have already ensured, presumably by AT command.

Is there any need for bonding at all? Is there a best practice for working with BLE device?

All blueteeth need to be paired by master to slave. That is the way Bluetooth works, but it only has to be done once and thus hardly worth questioning anyway. There is no "best" practice for working with BLE, only the correct practice.