If you are using Debian stretch with BeagleBone Black at least some of the images include test code that will run automatically when a barcode scanner is plugged in. (this was interesting to troubleshoot, lol)
To my knowledge this was not present on any Debian 8.X LXQT images.
You will know this is happening when at bootup instead of LXQT desktop showing up you will see a test screen instead with various image test patterns on the screen.
The simple fix is to remove the beagle-tester app and the associated script that runs it. (note the sh script has some device tree examples that might be helpful to look at as examples)
#Remove beagle-tester so that barcode scanners can be used. sudo rm /usr/sbin/beagle-tester sudo rm /usr/sbin/beagle-tester-open.sh
There probably is a service or 2 that are related to this, but removing those 2 files is at least one way of solving the issue.