Inky Frame RTC Wakeup Problem

I’ve a new Inky Frame 5.7 and am trying to essentially replicate the photo gallery example with some tweaks.
The idea is that the chooses a random photo from the SD card, displays it, then goes to sleep for a while.
This all works fine except that the RTC wakeup never seems to happen. Manually restarting the Pico or pressing one of the front buttons to generate a hardware interrupt gets it to run, but left to its own devices the system won’t wake.

Relevant code from

import inky_helper

activity_led = Pin(6, Pin.OUT)

#do stuff

What am I missing?

Turns out that even whilst using inky_helper for sleep stuff, I still needed to hold VSYS while running to stay awake.