I've been testing some upgrade scenarios for Version V7 with beta4 being the current beta release.

Tests were conducted on:
RB4011
RB1100AHx4
cAPac

All 3 routers were "No Config" resets so they have no odd configuration present.

6.44.6 -> 7b4 - Bricked on all 3 routers. Proceed to Netinstall
Netinstall to version 7b4 failed with netinstall tool of 7b4 and 6.44.6
Netinstall to version 6.44.6 worked perfectly.

6.46.2 -> 7b4 - Bricked on all 3 routers. Proceed to Netinstall
Netinstall to version 7b4 failed with netinstall tool of 7b4 and 6.46.2
Netinstall to version 6.46.2 worked perfectly.

Interestingly enough, when going from version 6.44.6 or 6.46.2 to V7b3, there are no issues.
Then going from V7b3 to V7b4 --- It works!

A curious upgrade path to follow for those who are having bricked routers after going from V6 to V7b4

If I've missed anything or should test on other models or versions, let me know.
New versions come with fun new problems.

I have successfully upgraded two Cloud Core Routers (1036 and 1016) from 6.46.2 to v7 B4. I also tested my RB750GR3, 6.46.2 to v7 B4. I have had some issues with going backwards / downgrading and that was v7 B3.

Regards,

Eric