ble nano 2: data is lost when transmit

[laterrps]

Hi i have an issue when i transmit string less than 20 bytes data is sent correctly but when i send bigger data packet data is lost even when from android application packet are splitted into 20 bytes packet or less sometimes data is lost even when i add a delay between packets. For example if i send a string "Hi this is a test" data arrive correct but if i add "for detect the bug" (string complete "Hi this is a test for detect the bug") sometimes arrives correct but in other cases bytes are lost -> "Hi this is a est for detect te bug" or similar cases i don't understand the reason why is this happening, can you help me?