Mouse and keyboard

Keys landing on the wrong computer, stuck keys, clicks in the wrong place.

My typing goes to my own computer

Keyboard grab is off. Toggle it in the toolbar or press ⌘K. The toolbar shows which state you are in.

On a Mac, grab needs one permission: System Settings ▸ Privacy & Security ▸ Input Monitoring, switch RealFrame on. Without it, grab looks like it does nothing.

Ctrl-C does not stop a running command

Your ⌘ is being delivered as the far computer's Ctrl, which is what makes copy and paste feel normal, and what gets in the way in a terminal.

Turn off Session ▸ Use Mac Keys and Ctrl chords pass through untouched. See keyboard.

A key seems stuck down

Press and release that key once on your own keyboard. The far computer reconciles modifier state as new input arrives, so one clean press clears it.

Clicks land in the wrong place

A display-mode mismatch. Try, in order:

Switch display mode once and back (⌘1 then ⌘2).
In Fit, check you are not clicking inside a black bar. That is outside the far screen.
If the far computer changed resolution during the session, reconnect so both ends agree on the size.

Nothing responds at all, but the picture moves

You were let in to watch, not to drive. On macOS that is a missing Accessibility permission on the far Mac. See permissions.

Ctrl-Alt-Del does nothing

It is in Session ▸ Send Ctrl-Alt-Del, deliberately without a shortcut. On a Linux desktop that combination logs the user out instead, so the menu item is aimed at Windows.