Deactivate / undo merging of two-parter

I just searched nearly 15 minutes through all my folders because I thought some of my files had vanished until I recognized, that some of the episodes were twice as big as normal...
Is there a way to undo the merging of the two files? And can the merging be deactivated or is it not automatic and I just did it by accident myself?

This app changes the names of files and can also move the files - it cannot merge files. Something else is going on in your system.