Post your Dolphin settings. Click the config button and look at the General tab. Click the Graphics button and look at the General, Hacks, and Enhancements tabs. We'd prefer it if you provided these as screenshots (google how to make them if you don't know).
Are you trying to play both MP4 and MP5 using netplay? The official stable release (3.0, not sth like 3.0-809, just 3.0) tends to have less issues desyncing, based on user reports. There is a netplay guide on the forums (check the sticky FAQ thread for a link) detailing the best settings you and your friend should use.
It could also just be your dump. Use a program to generate an MD5 hash for your game files (there are plenty of free tools, Google knows). Once you get the hash, compare that to one provided by online databases like GameTDB or Redump.org (make sure the regions are the same, it makes a difference). If your hashes match up with theirs, your dump is okay. If not, you'll need to redump your game until the hashes match.
Are you trying to play both MP4 and MP5 using netplay? The official stable release (3.0, not sth like 3.0-809, just 3.0) tends to have less issues desyncing, based on user reports. There is a netplay guide on the forums (check the sticky FAQ thread for a link) detailing the best settings you and your friend should use.
It could also just be your dump. Use a program to generate an MD5 hash for your game files (there are plenty of free tools, Google knows). Once you get the hash, compare that to one provided by online databases like GameTDB or Redump.org (make sure the regions are the same, it makes a difference). If your hashes match up with theirs, your dump is okay. If not, you'll need to redump your game until the hashes match.