It appears to be common... everyone that I know who owns front-load washers has this issue... It smells like moldy farts. I have tried using those commercially available washer cleaning pucks, but they seem to make it worse. I have been leaving my washer door open between loads lately, and the smell seems way less pronounced, but still there.
It may be the fabric softener. It needs to be diluted so it will all rinse away. Some brands have made theirs thinner to prevent this.
Ours recently smelled like a sewer back up. I took off the bottom panel and cleaned out the trap. (it's completely gross) Took care of the smell though. Also, wipe down the rubber gasket every so often and make sure you don't have any socks trapped under it.