Elements dissapearing between sessions when using mesh splines

Hello! I have encountered a strange problem that I am not 100% sure where the issue comes from. I have noticed this problem mainly when selecting elements outside of the default folder for the mesh spline editor (for example, I imported a fence mesh from the industrial level folder into my save file, and am able to use it just fine with mesh spline and with asset browser). Everything will be fine in this first session, exactly as I had placed it. But after saving the file and closing, it will sometimes only save about half of the spline for some reason? Some of the elements just dissapear as if I had never placed them, while others remain on the same spline. My best guess is that when I make a new spline in a session, it sequences elements by numbers, and that the old spline numbers overwrite and conflict with the new ones, causing only new spline number elements to exist? All the splines I am showing have come from different sessions that I have worked on my level. Mods are not a factor, it has occurred independently of that factor.
Here is an example:

I had ran the spline on top of the brick mesh road all around, and yet only this small portion of the original spline remains. It is strange because the missing elements are not even in the scene tree.
Here is another example (this time with alternating elements):

Only my first mesh spline I made is unaltered (and it uses elements outside this default folder, so this might not be the problem at all?):


Thanks for looking into this, I hope this is enough information to help solve the problem!