Textpad 8.1.1. (Demo) ist not working

[HL1234]

I'm testing Textpad 8.1.1. because the old Licensed Version of Textpad 7.6.4 can no more change the date of a file on my NAS if it is edit. Notebook++ does that correct. But with Textpad 8.1.1 there have many errors:

Open a text file with doppel-click does not open it.
Then I loading the file with moving it with the mouse to TextPad.

Saving the changed file give the error "An other program has changed the file .. New load?"
I say yes: Message Box "Unknown Error".

Closing then the text file without saving - the file is now empty. 0 bytes Such text-files-killing editor I will not buy.

Have you any help to fix that?

At the installation of TextPad, 8.8.1 it hasn't recognize that an older installation is on the system so I installed TextPad, 8.8.1 in the same place where TextPad 7.6.4 was installed.
I do so because I like not to lose all my settings.
I could first deinstall TextPad 7.6.4 if there is a way to save all my Configuration setting within TextPad?

I could live with the old licensed TextPad version 7.6.4. But the problem is, that I figured out, that if I edit a file on my NAS and save it, the alteration date does no more change.
Do I change this file with Windows Notepad, Write etc.. the alteration date is changing to now. I'm using Microsoft Windows Version 20H2 (Build 19042.1110). Before I would buy TextPad 8.8.1, it must be sure that this error has been fixed.

The support doesn't answer anymore - is there any help?