Renaming a file (by pressing Enter) removes extension also!

I have mac OS High Sierra ver 10.13.4 on my MacBook Pro. I have enabled "Show all filename extensions" in Finder > Preferences, which shows extensions of all files in the Finder windows.

However when I try to rename some files (e.g. Screenshot .png files) by pressing Enter on the filename, it asks me "Are you sure you want to remove the extension?" after entering the new name. But for some other type of files (say documents), it lets me edit only the name part of it also showing its extension. See some screenshots below.

1. Lets me edit only the filename also showing its extension:

2. Shows and lets me edit only the filename, without showing its extension (its original filename is Screen Shot1.png):

If I press Enter here, it asks me if it's OK to remove the extension. If I say No, it doesn't rename it. But I don't to say Yes either for it removes its extension. Any solutions to this annoying issue, please?