I found this issue with an second batch of a small Toy Robot.

This robot consists of some Motors and an Atmel MCU togheter with an JDY-23.
The first batch had the exact same Hardware, but the Firmware on the JDY-23 was slightly older.

Overall i was able to verify the new JDY-23 Firmware, by manualy sending RemoteXY Connection Requests:
55 06 00 00 F1 E9

Received:
55 DC 00 00 13 00 00 00 00 1F 01 6A C8 01 01 05 00 48 00 21 6A 6A 0C 0C 00 5D 1A 00 00 C8 C2 00 00 C8 42 00 00 00 00 05 01 5F 68 68 20 06 1A 1F 47 05 36 30 30 38 0B 08 02 91 00 00 00 00 00 00 48 42 00 00 20 41 00 00 A0 40 00 00 80 3F 18 54 65 6D 70 65 72 61 74 75 72 20 C2 B0 43 00 06 00 00 00 00 00 00 70 41 0C 00 00 70 41 00 00 0C 42 24 00 00 0C 42 00 00 70 42 0A 02 01 65 1F 31 04 01 1F 41 75 74 6F 70 69 6C 6F 74 00 1F 4D 61 6E 75 65 6C 6C 00 47 35 36 30 30 38 03 08 02 91 00 00 A0 40 00 00 10 41 00 00 80 3F 00 00 00 3F CD CC CC 3D 18 42 61 74 74 65 72 69 65 20 56 00 01 00 00 A0 40 00 00 B0 40 5E 00 00 B0 40 00 00 C0 40 0C 00 00 C0 40 00 00 10 41 30 71

Which according to Modbus CRC16 is a valid responce.

Communication between Robot and Smartphone (Android) was logged using an Logic analyser on the RX / TX Pins of the Bluetooth Module.

The Used BLE Service:
0000FFE1-0000-1000-8000-00805F9B34FB
Is also the same as some HM-10, and works just fine if used with the "BLE Scanner" Application.
-> I can also writhe the Service Manual, and receive the data as above.
Using anothe BLE Terminal App also yields the same result.
The Communication is definetely working.

I noticed something interesting:

23:31:42.557 App version 4.15.09, API 34
23:31:42.589 Pending device ...
23:31:42.598 Device started
23:31:42.598 BLE connection started
23:31:42.598 Connecting to BLE device 19:15:F0:18:E9:22 ...
23:31:43.579 HM10 UART Service found
23:31:43.630 BLE device connected
23:31:43.650 Receiving GUI configuration...
23:31:48.657 Read timeout error
23:31:48.657 Receiving GUI configuration, try 2 ...
23:31:53.664 Read timeout error
23:31:53.664 Receiving GUI configuration, try 3...
23:31:58.671 Read timeout error
23:31:58.672 Receiving GUI configuration, try 4...
23:32:03.681 Read timeout error
23:32:03.681 Board not reply.
23:32:03.681 Disconnect
23:32:03.705 BLE device disconnected

The App tells me every 5 seconds that a retry is happening, but i see nothing on my logic analyser.
If i use the manual way (BLE Scanner, BLE Terminal) i see communication going on.

Is the Retry defective?
What could be the issue?