Ch always writes cell phone individually, why?

No matter if I write somewhere else on Whatsapp. Often when I want to write something with sch or for example "Oh" he writes it to me with s cH loss. Here I used the word "castle" as an example. But not always. For example, if I want to see how that happens, it doesn't happen. Maybe someone can explain to me how this happens. Can you turn that off somehow?

My cell phone is a Huawei Mate 10 Pro. If it has anything to do with it.

Incidentally, it can't be anything that automatically replaces the word, because that is switched off and is not to be found in the suggestions anyway.

Maybe you press the spacebar at c at the same time?

Not really. I've tried to re-enact, but somehow not. If only then comes the c and the dial tone is always before the C and then after the H. And the H is also capitalized.

Then I have no idea now, unfortunately