Firmware upgrade after Eero upgrade

Hi,

I had 2x Eero Pro 6, and replaced these with Eero Pro 6e. Here's the procedure I followed:

- Upgrade gateway first using the "replace" option in the app

- Upgrade the firmware

- Upgrade second Eero Pro 6e

- Tried to upgrade the firmware

I am saying Tried, because it doesn't work. The system either keeps on rebooting itself, or seems to be stuck. For now I somehow have both nodes stable, although one at v6.9 and one at v6.7.

Can I leave it like this until the next firmware is pushed? I really can't seem to update the secondary Eer Pro 6e