ADILBTDon't know what happened but it should be fine for you to upgrade to A11 again. Whatever issue your phone had which caused a bad update is not gone. Downgrading to A10 rewrites all files while an upgrade to A11 only updates the necessary files. So the "damaged" files which caused this issue, are now replaced.
I told my self the same thing when i read people's problems, until it happened to me too ..
S4tI've created a case. Thanks!
I believe there's something wrong with the latest Android 11 update (WW-18.0610.2104.145).
I never had the boot loop issue, but since upgrading to this version, my Zenfone 6 (128GB/6GB/UK) already got stuck in a loop after rebooting 3 times. It starts, shows the ASUS logo and then reboots. Even worse: most times it boots well, but sometimes it loops.
The fix I found was to keep the phone charging and let it boot loop. Eventually - it can be 5 or 20 minutes - it seems to change to a different partition and boots normally.
And it seems I'm not alone. You have this post, but there's also 3 posts on the reddit sub made in the past week or so. For example, this one says that the "Update failed, reverting to old system". On this post, a different user reports bootloops after the latest update and mentions that it also starts after ~15 minutes. Another user reports the same problem after a reboot. To make things worse, we can't downgrade to the previous update without a factory reset.
In my case, I am unlocked and rooted, so maybe I'm not the best example, but these reports are from users that don't do this.