Hello there
The screenshot dialog is my child
I take all responsibility for bugs
I have made some changes in BL 5 to screenshot setup. So, let's have a look.
Firstly you have to be able to open the settings. Press Alt Esc to bring launcher on the screen and begin typing "screenshot setting". Open it. This is the settings window
https://i.imgur.com/M1jESSV.jpg
Then check out the application for opening the picture. If you have Okular or Mirage there, OK. In case you need to open with default one, write xdg-open.
Then you can set up also your grabbed picture quality with the slider. Set it up as you wish.
Also, set up your destination folder for saved pictures. Desktop is default.
Now, the other part of your question. Opening pictures twice. Hmm, I am not sure but I dont remember I had this issue with BL 4.5. I can try it under Virtual box and will let you know. In the meantime, set all stuff as I mentioned above and let me know if it help.
Stefan
PS: to be proper, I can also explain why I added delay for taking picture. It is because of grabbing the menus which disappear in case of time 0 s. I do it this way: launching screenshot, prepare the menu scene and after some seconds the picture is taken. Enjoy