Escape + number performs actions other than switching to window by number

[Dun Peal]

Hi folks,

I just upgraded to Ubuntu 18.04 from 16.04, and noticing an odd
behavior with the key combinations that used to switch windows by
number.

In 16.04, if I held Ctrl and hit the escape key, and immediate after
it a number key (without releasing the Ctrl), I was switched to that
window number.

In 18.04, if I do the same, in some cases a different action is
performed. For example, if I hit escape-3, it executes the `copy`
command (i.e. activates Copy Mode). Escape-4 triggers `quit`. Escape-5
triggers `paste .`

Some switches still work fine as before, for example escape-1 and escape-2.

Also, I still get the previous switch behavior if I release Ctrl after
hitting the escape key and just before hitting the number key.
However, that is slow relative to now having to release the Ctrl, and
if I'm not careful I still get the undesirable action.

Is there a way to get the same behavior as before, such that hitting
escape + number will always switch to that window, even if I didn't
release the Ctrl key?