"Leaf" AMS mirror lag behind

Hi all, I have a problem with the mirror on my “leaf” AMS servers.
Let’s describe the current setup:

1 Win2003SRV at the center , MSDE + ADNM v. 4.7.531
4 Win2000SRV at the periphery , MSDE + ADNM v 4.7.531

All 5 servers use the same proxy to access the internet and to get the updates, and all 5 have the correct proxy settings in Control Panel → Add/Remove Programs → Avast! Management Tools → Proxy Settings

The problem is that the mirror of the central server is always up to date , and instead the periphery servers are always or almost always lagging behind, even weeks.
To force the mirrors to update I have to:

  1. manually login to each server through remote control
  2. log to the ADNM console
  3. go to the mirror settings (settings → mirroring) and disable / re-enable the mirror

At this time the mirror process restarts and completes successfully.

I have to manually re-do this each day.

I even tried to schedule a simple batch file to stop-start the mirror service ( net stop aswHTTPMirror + net start aswHTTPMirror )
but it doesn’t seem to work ( the service gets stopped and restarted ok but the mirror remains out of date ).

I thought about updating the ADNM version, but before doing that I keep wondering why the central server does always get updated??

Also, In case I decide to update, am I forced to update all of the 5 servers at once or can I try the update only on one to check and test if it resolves the problem?

I hope that someone with more experience can solve this dilemma!

Thank you in advance,

Michele