Hello,

We have recieved a lot of routerboards 951Ui-2HnD and RB2011UiAS-2HnD
they have ROS 6.18, and then I downgrade to any 6.x License become Level 0 and software ID after any reboot is different.
If I import earlier exported license - ROS say it's invalid
I tried netinstall to 6.x versions - but no success

Then i upgrade to 6.18, all works like a charm

P.S. Customers will buy routerboards only if routers operate at ROS 6.5, since their devices works only on this version.

Thanks.

Official statement of mikrotik was repeated many times here: don't downgrade below the version that was device shipped with as it may not work.