Printing from QL-7xx and QL-8xx series printers causing app crashes on Samsung galaxy tab

[joelsuite]

Context

For some of our users, printing over both bluetooth and wifi from Samsung galaxy tablets using QL series printers sometimes causes a fatal exception resulting in an app crash. This crash occurs when printPdfFile is called on the Printer object. The exception thrown is a NullPointerException. The cause appears to vary. The following are two examples:

Example 1

Model: SM-T500

NullPointerException
Attempt to invoke virtual method 'boolean java.net.Socket.isConnected()' on a null object reference

Stacktrace:

com.brother.ptouch.sdk.connection.WifiConnection:101 in startConnection
com.brother.ptouch.sdk.connection.WifiConnection:7 in open
com.brother.ptouch.sdk.Printer:85 in init
com.brother.ptouch.sdk.Printer:96 in printPdfPage
com.brother.ptouch.sdk.Printer:6 in printPdfFile
J2.E0:149 in j
t3.a:9 in resumeWith
K3.D:115 in run
J1.i0:196 in run
R3.k:3 in run
R3.b:94 in run

Example 2:

Model: SM-X200

NullPointerException
Attempt to invoke virtual method 'java.io.OutputStream android.bluetooth.BluetoothSocket.getOutputStream()' on a null object reference

Stacktace:

com.brother.ptouch.sdk.connection.BluetoothConnection:26 in getStream
com.brother.ptouch.sdk.connection.BluetoothConnection:41 in open
com.brother.ptouch.sdk.Printer:85 in init
com.brother.ptouch.sdk.Printer:96 in printPdfPage
com.brother.ptouch.sdk.Printer:6 in printPdfFile
J2.E0:149 in j
t3.a:9 in resumeWith
K3.D:115 in run
J1.i0:196 in run
R3.k:3 in run
R3.b:94 in run

I'm unsure how much of these stacktraces are useful, but they shows the errors originating inside the Brother ptouch library.
We could be implementing the another brother package in a way that is causing this, but without an error message that is meaningful for us it's hard to debug this.