The solution that ajeh offered is the way to prevent these issues...
I thought that there was a way to also copy the setting(s) (default/display only to an option value) to other places that option value is used (making the process quick) or of course a sql statement could be run to add that "feature" to all equivalent option values.
What I described above would not solve your problem. It does sound like there is need to apply the default and display only option to your Please choose... option value (best to be sure that it is the lowest non-negative sort order so that no other option can be the default causing the problem above.)
See this FAQ:
https://www.zen-cart.com/content.php...to-my-products
and take note of the section that says: