If you have a floor drain it needs to be kept wet to keep the trap charged. My plumber put in a hose from the laundry room sink water supply to the trap, with a little gizmo that lets a drip through every couple minutes. If you don't have something like that you should put some water down the drain more often, like once a week. More often won't hurt anything - the excess goes down the drain after all.

It may be your washer and not the plumbing. I have the same problem. Every few months, I rinse the machine with bleach and hot water.

We had a similar problem long ago. It was indeed the floor drain causing the problem.

Ours is located behind the washer and is not readily accessible. A little known trick which solves the problem virtually permanently is to pour an adequate amount of full strength standard automobile antifreeze into the floor drain. Last time I did was years ago and no problems since.

I used about 2-3 cups to insure a complete job.

Also, if you happen to have bathroom facilities in your laundry room, the wax seal on your toilet can allow sewer gas to leak. I've seen that happen more than you would imagine. The fix is a new wax ring, about 2 bucks, and 15 minutes to replace.

Good luck.

Such drains are typically associated with an inexpensive device required to be plumbed in with them. The device keeps the trap full and nothing more. (Sorry, don't recall actual name of this device but they are quite common) Your "dry" drain may have one of these that has ceased functioning properly. Usually found in a wall near the drain. If it doesn't have one, it should.