I ignored Emacs 25 because of this for a while now and used Emacs 24 but now I have to switch...
So here is the problem: I have a different keyboard layout than default (Colemak) and the key combination C-M-b (for example) inserts some unicode character (˘). Emacs 24 ignored this and executed backward-sexp as I wanted it. In Emacs 25 though the key is taken literally and inserts the character. I did not find a way to overwrite it.
I tried (global-set-key (kbd "C-M-b") 'backward-sexp) and (global-unset-key (kbd "C-M-b")) but neither had any effect.
If I run C-h k C-M-b (the describe-key function) it waits for more input, as if C-M-b was a prefix to some key.
Using (global-set-key (kbd "˘") 'backward-sexp) (which is ugly anyways) does not work properly either, because the ˘ character gets inserted only after hitting that combination twice, then it gets inserted twice, tough (as for all accent marks). This results in the command running twice and only if i press the key combination twice.
EDIT: This issue occures on Windows 10, on my Linux machine with the same keyboard layout it is not an issue.
How can I fix this? It's truely annoying. Thx in advance
I found out, how to fix this issue. Turns out that my keyboard layout had a so called "dead" key at that very key combination. I do not know why Emacs 24 did'nt struggle with that while Emacs 25 did, but the solution for me was to modify my keyboard layout and make that key non-dead.