The only difference between Beta 1 and this release is a few lines of scripting in vpnrouting.sh. If Beta 1 loaded fine, then your issue lies elsewhere.
I may agree with you to a point. That said, I believe I understand what may have occured. I would be beside myself to figure this one out or reproduce it.
Initially (Pre-Beta1) I was on 378.52.2.
I was on 52.2 as it was not causing any 5g issues in bridged mode.
I updated to beta 1 (I did not factory default) either the 66 or the 68 (As I normally do)
I updated to GA of 380.58
Factory defaulted using the pin hole after the update and both routers reverted to recovery.
ODDLY the ODD Part I
When I was able to get the initial modems back to 380.58 The main (68u) worked with no issues
The 66u however was the primary issue. Using the pin hole I made several attempts to clear the brick. 30/30/30 method did not work nor did the recovery web page as the router would not respond. I finally got the router booted after re flashing with asus 3.0.0.4.378.4585 and became stable.
ODDLY the ODD Part II
I then defaulted using the web GUI (not pin hole) that worked
I skipped wizard and updated to 380.85
I pin holed
The Router Bricked again

Now, when I pinholed it it came back to the original 3.0.0.4.378.4585

I cannot understand that at all.
I defaulted it this time again in web GUI
Updated to 380.85
It came up
When I bridged the 66 at that time it went off the grid, I could not find it, reach it without getting into one of the LAN ports and I was getting the default IP 192.xxx.blah.blah
ODDLY the ODD Part III
This is what I believe was going on.
After 2 days of mucking with the 66 I discovered when I entered the Bridge Password (On the 66) to connect to the mother ship (68) it was not taking.
I know I typed it in, I know this because I selected show PW
During my attempts I never looked at this and took no notice of the pre-filled in *********** in the PW field. I hi-lighted and wrote over. HOWEVER, my last attempt I changed it did its connection and I loose it again
I logged back into the 66 and check the Password it was not my 5g password, it was the web gui admin password.


How in the hell was this happening? I do not know. I write snap shot notes when I do things like this so I reviewed (Thus the above Novel)
Anyway, How I got around it
downgraded both routers to 3.0.0.4.378.4585 web gui defaulted both twice. Updated to Version 3.0.0.4.380.1842
web gui defaulted twice (Ya over kill) seems pin hole is an issue with me routers not trusting that.
Everything is fine at this point as I updated as well this morning to 380.85 Not going to factory default anything at this time