The picture below shows a retaining wall. It was hard to take a picture from a good angle, but it looks to me like the wall is showing a "belly" and the seams are opening up. But I'm not sure: perhaps it was built with these bulges. There's a lot of cement in this wall.
This wall in a Philadelphia suburb and it supports a patio on a very steep decline.
But I do hope that the experts here are able to assess from this picture!
The wall may have been built that way but I doubt it, the wall may have shifted over the years and is stable now.
The only way to know is to drop a plumb bob from the upper decking just in front of the wall and measure the gap at top middle and bottom. Mark the spot or leave a nail or screw in that location and Mark the wall at the 3 points so you can measure again at a later date. If the wall is stable you will see no change in the measurements.
I would not expect to see any movement in a year, but probably would recheck a week after a big storm. There looks to be a drain but water may have caused the shift or belly in the past, prior to everything settling, and now the wall is stable.
