Notepad typing problem from spellcheck I suppose

After upgraded to Windows 11, the new Notepad and other MS apps I use I observed the new functionality to save the file and to have it after restart, even if not saved. That's ok.

But, using daily notepad, and typing a lot sometimes in it, I observed a bug recently. Because I blind-type, I observed when typing some characters did not appear, even if I certainly typed them. 
Normally I just ignored and insisted to type the missing character(s). But after a time because this phenomenon repeated, I tried to view what can be the problem. In MS Word all normal. But in notepad it kept not registering some characters ...and that randomly, not because maybe I have a keyboard problem. Not at all. I tested that also. As I said, in MS Word all normal, but in notepad not. 
I observed also that the spell check works in the new notepad, but you don't have the possibility to activate/deactivate or simply change the language from the app config. I assume they are simply inherited from the Windows 11 general configs.
So after that, I supposed that this could be the problem. More exactly the source of the problem could be the spell-check. And I explain. 
For a simple test, I made a new notepad file and in that new notepad file I didn't had typing problem ...till some time. 
I say this, because I use a "note" notepad file every day, adding things always on top of it. So after some time it became big (at least big for a notepad point of view). 
So I suppose the typing problem in notepad is ...when it became big the spellcheck is allways trying to recheck all content and till not finishing the recheck the typing doesn't work normally (because in background the system is "occupied" with something else that is prioritized - i.e. with spell checking all the big file content).
I assume that in MS Word the things are differently, and it does not recheck allways all the content, or maybe has different resources allocated for that process so that it doesn't kill, or suspend sometimes, the typing process.
Corect me if I am wrong.
But that is what I observed.

PS. As a solution for me for that, I began to use for the big files the MS Word again, and for notepad olnly small files or opening new file for typing something ocassionally and then just copy/paste what I just typed back in the big file.