Hi
ZitherThank you for your asking. Based on your screenshot in Recovery Mode, I noticed that firmware version you had installed is WW-16.2017.2009.087. Did you downgrade your firmware by installed this firmware image file?
Please note that Android 10 to Android 9 downgrade steps can only be performed by installed Version MaxProM1_downgrade_to_9 image file, which leads to firmware version WW-16.2017.1912.060.
May you share your downgrade steps to me for further checking? If you have any concern, please upgrade to Android 10 beta WW-17.2017.2008.432 then follow the steps below as 10 to 9 downgrade steps.
1. Download "Version MaxProM1_downgrade_to_9" and then put the image file into the root directory of the MicroSD card.
https://www.asus.com/supportonly/ZenFone%20Max%20Pro(M1)(ZB602KL)/HelpDesk_BIOS/2. Insert MicroSD card into phone and then power off the device.
3. Long press with "Power" key and "Volume Down" key together and stop after feel the vibration to enter Recovery Mode
4. Use "Volume Down/Up" key and press "Power" key to choose "Apply update from external storage"
5. Select the downgrade file
6. When the updating process is done, Choose "Wipe data/factory reset" and tap"Yes" to perform the master clear.
7. "Wipe cache partition" > "Yes"
8. "Reboot system now"
[Phone] How to downgrade OS version from Android 10 to Android 9 target version? | Official Support ...