How to handle a bathroom fan with built-in humidity sensor (where switch on doesn't always mean fan on)?

I've tried several approaches but none of them seem to be reliable. Here's the scenario where I could use some extra eyes and thoughts:

• There is a built-in bathroom vent fan that...
  • Has an integrated humidity sensor that prevents a simple "switch to on" from always turning on the fan
  • Can be forced to on, but only if manually and quickly switched on -> off -> on in about 1 second
• I placed an energy monitoring Zigbee smart switch as the wall switch for this fan (a Jasco / Enbrighten Model 43078)
• A stand-alone zigbee PIR motion sensor has been placed in the bathroom as the trigger for this scenario...
  • When the PIR sensor is triggered...
  • Wait one minute
  • Turn on the fan
  • Leave the fan running for 10 minutes
  • Turn off the fan

So far, I've built an automation that uses the PIR sensor to start this scenario, a script to run a loop attempting to turn on the fan and watch for changes in the wattage to determine if the fan really turned on, and another script that does the On -> Off -> On behavior with a 1 second delay.

As you might guess from this post, it isn't working, or more correctly, it doesn't always work. There are times when the fan switch state is left on and the scripts don't account for that, and other times when the switch is off, where the script runs but for whatever reason the timing doesn't work out and the fan never comes on.

Because this is so maddening, and because replacing the vent fan isn't feasible, I'm reaching out to this group to see if anyone has seen a scenario like this before and if you have any suggestions of where to look next?