App works only with current version but not later

I just need some understanding here. I use this journal app called Day One and have recently upgraded the version. Somehow the updated version doesn't work, with the pop up saying "quit unexpectedly".
I went to preference in the library folder and had to delete a .plist file in order for this updated version to work. NB. the version I used before was working.
I'd like to understand why I had to go through this step for an updated application to work.

justperry said:

Probably bad coding on the Developers side, nothing you can do about it except sending then an email.

Click to expand...

What if I download an updated app that's from a third party? i.e. not from the mac store, and I have to go through the same process of deleting the file under preference. What would this deleting mean?