Adding elements causes "Gradle reobfJar task failed!"

Ooookay, I'm getting a little frustrated. Whenever I make a new entity / element, as soon as I run the client or regenerate code, it causes the error "Gradle reobfJar task failed!". It said that my files contained non-Ascii characters yet I haven't added ANY of them. I tried regenerating the code again but it shows the error.

I tried restarting my computer, and it did indeed solve the problem but like I said at the start, it would compile and throw this annoying error at me.