Hi to all,
ROs 6.19, RB433AH

I usually login through winbox, but suddenly "authentication failed".
Username and password saved in winbox, so I suppose an hack.
I login through webfig (same user) and I can logon.
Under "resources" I can read "bad blocks" = 0.1%.
Could be this?
Should I change RB before it will crash completely?
Thanks.

6.19 is very old and the device is likely hacked, you should netinstall a secure version.

Upgrade your device to latest stable or long-term RouterOS version, Winbox should be upgraded too.

Absolutely no way problem could be created by bad blocks?

According to the manufacturer of NAND chips, up to 5 blocks can be bad when NAND is manufactured, and up to 80 bad blocks could develop during operation, but it will not disturb the operation of your router, because complex workaround mechanisms are in place, that will copy the data to another block and attempt to fix the bad block.

https://wiki.mikrotik.com/wiki/Manual:R ... bad_blocks

My guess is that your Winbox version is too recent to authenticate on 3.19. As the colleagues said, upgrading your ROS should be the first step, but just to login you should be fine with an older version of Winbox.