[Agda] Certain Emacs commands not working; being reported as "undefined"

[Dave Martin]

I have Agda 2.5.3 and Emacs 25.2.2. (I use the text version.)

The following commands, and they alone as far as I know, do not work and are reported by Emacs as "C-c = is undefined" and so forth:

C-c =
C-c ?
C-c ,
C-c .
C-c ;

These are not typos; this--without the second cee-minus--is how the error messages appear for some reason. Meanwhile, most (often related) commands I have tried seem to work perfectly:

C-c C-l
C-x C-c
C-c C-x C-d
C-c C-f
C-c C-b
C-c C-d
C-c C-n

C-c C-SPC
C-c C-r
C-c C-a
C-c C-c
C-c C-t
C-c C-e

What might be the problem here?