Hello everyone. I noticed that after updating the firmware to 7.17, a strange symbol appeared in the current firmware field, similar to (U+2642 
male sign). Has anyone else had the same problem? What do you think it is? An Easter egg from the developers, a firmware glitch, something else?
Nice find 
This is because you do not align the factory firmware, and new firmware have some misalignment…
Install exactly 7.6, upgrade the firmware, reboot to be sure current firmware is 7.6 then install this:
https://box.mikrotik.com/f/3bd8cc7b2a6545228377/?dl=1
Next you can install correctly 7.17
https://help.mikrotik.com/docs/spaces/ROS/pages/40992878/RouterBOARD#RouterBOARD-Protectedbootloader
Thank you! I'll try and write what happens
Please tell me in what cases is it necessary to carry out such an alignment? For all old devices with old firmware? Or for certain versions of old firmware?
The Wiki page mentions:
If your RouterOS is v7, your factory-firmware version is lower than 7.6 and your device displays the message → The "protected routerboot" feature requires a backup-routerboot upgrade
If your RouterOS version is v6 and you get the same prompt
I do it as standard procedure on any upgrade, but as soon as it is referrred to in the release notes you should.