This problem has already been reported on the official github website at the following link https://github.com/ckeditor/ckeditor4/issues/4252

And they come to the conclusion that it is a browser error.

I am having trouble using CKEditor. Every time I press the enter key on Android it closes the keyboard. I have to press / click the editor again to open the keyboard. Can this be prevented?

Please help. I’ve been looking for an answer everywhere, I can’t find the answer. Thank you.

I tried on this demo page the results were the same.
https://ckeditor.com/ckeditor-4/demo/