Sound like you did everything right.
- Updating after oos flash ensures oos on both slots
- You are indeed using the latest platform tools
I think you made the same mistake I made the first time. A little impatience. Mine went into crashdump as well.
When you perform the fastboot update command, the phone reboots to fastbootd during install (red fastboot letters) after the first 2-3 minutes. It looks like it is done, but don't touch it yet!! It is actually still installing. It will say on your PC when it's done. For me it took about 5-10 minutes.
Only perform the factory reset after.