Test.assertMessage not working on Side-Load

I have several assert statements throughout my app the first one being in the TimerHandler function:

function startUpdateTimer() {
    Test.assertMessage(updateTimer != null, "updateTimer uninitialized");

    var callBack = new Lang.Method(TimerHandler, :updateTimerCallback);
    updateTimer.start(callBack, CALLBACK_TIMER, true);

}

I have the using statement for the test module. This works during the simulator.

However when I side-load the prj onto my Vivoactive 4 I get the following warning:

Error: Symbol Not Found Error
Details: 'Failed invoking <symbol>'
Time: 2020-07-07T20:14:22Z
Part-Number: 006-B3224-00
Firmware-Version: '4.70'
Language-Code: eng
ConnectIQ-Version: 3.1.9
Filename: RefWatchPlus
Appname: RefWatch+
Stack: 
  - pc: 0x10002c42
    File: 'D:\Programming\garmin_dev\RefWatchPlus\source\TimerHandler.mc'
    Line: 20
    Function: startUpdateTimer
  - pc: 0x10001603
    File: 'D:\Programming\garmin_dev\RefWatchPlus\source\UI\RefWatchView.mc'
    Line: 35
    Function: onShow

I have confirmed it is the Test.assertMessage function using System print statements. Additionally, the App works correctly when built for release and side-loaded.

Any guidance on this issue would be appreciated.