Best answer by rikkster
You should be able to login to Dropbox and see when your files were last uploaded. A factory reset generally clears up most software related problems. Your best option is to factory reset your LG G4, if the problem persists, then there's the possibility that it could be either a software or hardware related issue.
If the LG G4 is within the manufacturers' one year warranty period and the software has not been tampered with, (e.g. custom ROMs, root, etc) and there are no signs of physical damage, then Koodo will replace the phone if it's found to be defective.
If you have PC Sync/LG Backup/LG Bridge software installed on your computer, you should be able to backup most of your data this way. Do the backup again to ensure you've saved everything that needs to be saved. Another option is to connect the phone via USB and use the MTP (media file transfer) function to transfer photos and other media types to your computer.
You may not be able to factory reset the phone from the software side. Instead you'll have to use a combination of hardware buttons to perform the factory reset. Here's a short video that explains how to do this, if needed.