Jetson AGX Xavier H01 kit GPIO / PWM troubles


I am working with the Jetson AGX Xavier H01 kit from Seeed, running Ubuntu 20.04 / JetPack 5.1.2

I am trying to get some PWM output on any of the 3 PWM outputs on the 40-pin header.
First off, it seems that the pin #s printed on the metal enclosure are wrong, and that pin 1 as displayed here:
Is actually the pin with 39 next to it on the dev kit. Would be great if somebody could confirm this.

Second, I am unable to get a nice PWM signal out of any of the pins I’ve listed.
Steps I’ve taken so far:
1.) ran sudo /opt/nvidia/ and verified that PWM is starred for all 3 of the possible pins on the 40-pin header
2.) Ran the script from the Jetson.GPIO git repo. This caused a change in signal on Header pin 18 but it is not a square wave. Looks like high frequency noise on the scope.
3.) Manually messing with the pwmchipX Sysfs devices, setting duty_cycle and period values and enabling.

Seems I am missing something fundamental here. Any pointers would be appreciated.

Giving an update on this:

I still have not been able to get PWM working on any of the GPIO pins on the 40-pin header.
Seeed supplies a custom pinmux configuration for this dev kit, but unfortunately does not provide any design resources for being able to modify it to use things like PWM.

It would be great if somebody from seeed could weigh in here on how to do use PWM on Header pins 13, 15, or 18.