@Jonathan-Silva Hi! It’s probably a version mismatch. Make sure that the libs you are including contain the same version you were using before. If possible, update to the latest one. Monaca’s Onsen UI is not different from original Onsen UI, you can use any of them.
I don’t know if my choice could be “called” a good practice. But I have made one splash screen for each size. And i have no problem during the process. I’ll send you one package - D. App. So you’ll be able to check if it works to you or not.