Zebra QLn420 Disconnects After Single Label Printing

Hoping that someone can help me understand the issue I'm coming across.


I have hundreds of Zebra Printers in the field currently. Many are older than 2 years. I've just deployed three new printers and each printer is having the same problem - they lose connection with my software upon printing multiple labels. I've been wracking my brain trying to troubleshoot the configurations since my application (nor the iOS version has changed) then I noticed two small differences between the configuration of the 3 new printers and my in-house debug unit.


1. My debug unit (which works perfectly) is running Firmware V68.19.7 and utilizes Bluetooth v4.2.1

2. The new printer (which fails every time) is running on Firmware V68.20.01 and utilizes Bluetooth v4.3.1p1


In terms of configuring the printer, I do very minimal through the Zebra Setup Utility. Two small sets of commands.

The first to define my label settings




















And the second to define my bluetooth/connectivity

! U1 setvar "bluetooth.enable" "on"

! U1 setvar "bluetooth.discoverable" "on"

! U1 setvar "bluetooth.minimum_security_mode" "1"

! U1 setvar "bluetooth.bonding" "on"

! U1 setvar "bluetooth.enable_reconnect" "iOS_only"

! U1 do "device.reset" ""


On the NEW Printers I can connect via Bluetooth in the iOS settings, and show as paired on the printer. Then I can open my application and print a test page as well as calibrate the page size (we have two interchangable labels). But then when I go in to the actual data I'm printing (receipts, labels or tags) if I attempt to print more than one item in succession the printer shows as disconnected in my application but still displays as connected in iOS.


Since my application code has not changed - nor has the Apple iOS settings, my only thought is that it has something to do with the Bluetooth supported version on the printer itself. Is there come command that I could run to either roll back the bluetooth driver to 4.2.1 or a command that will stop from a disconnect while printing?


Any thoughts would be greatly appreciated.