Hi all
Is it safe to downgrade any older version than 5.1? just because newer boot loader was upgraded with 5.1.

thanks

Do not think you will have a problem. Did a downgrade to 4.17 the other day. Just make sure you have the package with every thing in it. (One package.)

newer bootlaoder versions can be downloaded from routerboard.com

to install these, easiest method would be to upload it to router, with /system routerboard print check if correct version is displayed as upgrade-version and issue /system routerbaord upgrade command, when prompted for reboot - do that. After reboot you should have bootloader version installed.