Look at the exported spline in a text editor. Pay attention to the first line of spline data, there is a good chance that it doesn’t match the rest of the data. This happens because of the settings used when placing your objects along the spline. The setting would be “No objects at start” or something along those lines. If the first line of data does not match the rest, it’s safe to delete it.

My advice would be the same, at least to start with. Make sure the spline is not rotated, make sure the data set is clean, Double check all the spline placement settings to make sure random y rotation or anything like that is turned on, and check the first line of the data set to see if it matches the rest. You may need to check the “no object at start” setting.

You can also try reversing the spline and running it from the opposite direction if everything else looks ok.