Same original EXE, 6 months apart, quite a difference in decompilation.

The code on the left was from an .EXE in December. That same .EXE today is on the right.

There are more files as well in the two main folders 

What could be causing this?

The December one works fine when compiling but the recent one does not as there are many errors. Over 400 of the same sort of error.