There are some floor guides that can be adjusted to fit various width doors, yours may one of them.

I checked it and there is no adjustment. You know the door came off the overhead track once. I put it back and it slides fine. Would it be possible that it is out of alignment at the top? But I wouldn't think that it should have so much room to move around at the bottom. If it weren't attached to concrete I would just take up the old guide and put a different one it, but we aren't real handy and screwing things into concrete might be a challenge.

Hi, Make sure all the wheels are on the tracks, check both doors. Also make sure the doors have rooom to move, too much stuff in a closet can cause the problem. The guide at the bottom very seldom causes that problem.
Good Luck Woodbutcher

What is the door thickness?

I just remembered that my linen closet has the same type of sliding doors. Looking at those doors there is no big play at the bottom where the door fits into the guide. These must be adjustable and I just am not able to see from this angle. I don't know what word to use, but the area for each door to fit into is fine on the linen closet doors. The bedroom doors are another thing. One door fits nicely in the alloted space in the guide. But the other guide looks to be spaced way to wide. So that is why the door is able to jostle around. How hard is to remove the screw holding it into the concrete and then screwing it down through the carpet and concrete in the new adjusted position. Do you need to do anything special to get it to screw into the concrete? Can I use the same screw? Sorry for being so home repair challenged.

There are those that have 3 nylon guides attached to an accordion web under the floor bracket which fit most doors and kind of free float within the limits of the bracket.
And there is another that has prescribed notches in the floor bracket which you insert the nylon spacers based upon the door thickness.
You can remove the screws to remove the bracket, do the repairs and reinstall the bracket, or replace it.

I don't know how to fix what you have, but I had a couple bi-fold doors that were driving me crazy. I replaced all the hardware with a quality brand of door hardware.

This is the kind of stuff that some builders cheap out on, and replacing the cheap stuff makes the problem go away.

Here is a link that might be useful: Johnson Door Hardware

Thanks for everyone's help. It is much appreciated.