When some UTF8 characters are put in /system/identity name (to be exact, I had a problem with letter “Ž”, didn’t investigate this much further) console (also ssh) crashes after trying to write something in console and error is shown: “Console has crashed; please log in again”. Seems to be v3.x and v4.x related.
Not really a huge problem, just wanted to save someone a few hours of upgrading/downgrading and banging their head trying to figure out why this is happening 
emmm, even the forum and firefox can’t display that mysterious character 
are you sure it’s UTF8?
Maybe your OS cannot display it? I can see it fine in Chrome on Ubuntu.
I can see and type “Ž” with no problems, but the OP posted something else.
ĀČŽŠĶŅĻÕĢ
Anyway, RouterOS only supports A-Z and that really shouldn’t come as a surprise
Well should have written non-ASCII character to be exact, but we’re really splitting hairs now, eh? Main point is - if you get that error, go check what is set in identity name…