We are following sergejs' advice to downgrade an RB133 from 3.30 to 2.9.51 to see if it will solve a problem with an AP which has the only Prism card in our network.

We encounter

system,error broken package routeros-rb500-2.9.51.npk

We would surely appreciate any advice on how to accomplish the downgrade.

kind regards/ldv

try to download the packages once again from here:
http://download.mikrotik.com/all_packages-ns-2.9.51.zip

could simply mean what it says