why ble(phone side)disconnect with 8 bytes lenght characteristic

[makouda]

I want to send a set of 64 bytes data with ble. as I understand, the max data length I can send within a characteristic is 29 byes. when I send 4 bytes data it works fine, but when I send 8 bytes data notification, it works one or two times then it disconnect. what's the cause of this disconnection

[Ole Bauck]

The maximum packet length in a connection is 20 bytes. Do you have any more information like disconnect reason or sniffer log?