I started having problems of this type two days ago, I think soon after an update to my Samsung 303C. This is after over one year of extensively using ssh on this machine with no such problems.
The cursor works fine for a minute or so of typing, then disappears, or freezes in the wrong place. The problem seems to start either after using a ctrl key sequence, or after running a program like top, emacs, etc. Just typing alphanumeric characters into the prompt doesn't seem to trigger the problem (but maybe I haven't tried long enough).
I am not on beta or dev channel, and never have been on this machine.
I tried powerwash and it didn't help.
Running in screen or tmux doesn't solve the problem (and doesn't cause it either as it can happen in the login shell too).
There seem to be no problems with pointer or keyboard use outside the terminal.
The same problem happens using crosh, or when using ssh launched from outside the browser.
All ssh options are set to default, and the problem happens equivalently when connecting to several destination servers.