OVR Metrics Tool (Native Mobile): setOverlayDebugString does not work

Greetings!

I am trying to add some custom debug info to overlay in OVR Metrics Tool and this does not work for some reason.
I am using OVRMetricsToolSDK.aar which is distributed inside OVRMetricsTool_v1.5.1.zip.

I've added this aar to my android project and this is how I try to set custom debug info:

MetricsService.bind(getApplicationContext());
while (true) {
    MetricsService.setOverlayDebugString(getApplicationContext(), "hello world");
}

This does not change anything on the overlay and I cannot see any custom text. Default overlay is running fine and "Display Debug Data on Overlay" is enabled.
I can also see from logs that Metrics service is running:
If I use MetricsService.appendCsvDebugString() instead, my custom text is logged, so I assume that communication with metrics service is fine.

Could you please help me with this issue? I would greatly appreciate it!
Thanks a lot in advance!