Here is my note from June 10th 2022.
I finally got time to look into this. Looking at the schematic of the power section, R107 and R108 create a divider that feeds pin 11 of the SY7215 part. Starting then turning off the system, I went to measure the voltage on the junction of R107 and R108. This caused the system to shut down. Found that odd, so I tacked a 1 Meg resistor on top of R108 to drop the 100K value just a bit. The meter should be about 10M so thought this would do it, it didn’t. I next reduced R108 down to 68K by putting in parallel a 220K resistor. This resolved the problem and the system now shuts down as expected.