I'm not sure what is supposed to be broken but sure was curious as I have a system which has mirrors extension running installed, mostly was curious but attempted to use it on an occasion when we couldn't connect to the main repository. Anyhow, the mirrors appear to be functioning perfectly on my system.
select any ftp from the mirror which connects fine, then after removing mirrors from onboot, the address return to default which works without issue.
tried again, this time installed abiword, after completion connection occurred as expected and proceeded to install another extension. Interestingly, after an app install the app browser windows do not go blank as Kramer describes, although I have recollection of a similar event in the past which iirc was resolved by simply waiting a few minutes and reconnecting.
Maybe I missed something..?