Your comments

Thanks for your suggestions, I do appreciate them. I was not aware that there are currently no beautify and minify tools for iPad and it would certainly be a good fit for Textastic.

Thanks for your feedback! I'll consider it for a future update.

It used to work, but I recently saw that at least in the latest iOS 11 beta it doesn't work anymore. I'll investigate.

Ok, so it seems to be a system-wide problem on your Mac. Maybe you could have a look at the Console app to see if anything suspicious is in the logs.

Other than trying a reboot, I do not really have an idea what might be causing this, sorry.

TextEdit uses the same mechanism to restore windows if the checkbox is unchecked in System Preferences.

Does TextEdit correctly restore windows?

Does a reboot help?

You can also try to delete the folder that contains the saved application state:

  • Close Textastic
  • Delete the folder ~/Library/Containers/com.textasticapp.textastic-mac/Data/Library/Saved Application State

Hmm, weird. 

What happens when you go to System Preferences -> General and uncheck the checkbox called "Close windows when quitting an app"?

That sounds like the Working Copy file provider extension crashes. 

Please try to reboot your iPad. If that doesn't help, please contact Anders Borum, the author of Working Copy and ask him for advice.

Yes, I've seen that. That's excellent news.