Bug: sections reorder themselves after update

When I make a change to a section (not a reorder) and update it, it reorders the sections.

In one instance, I had 4 sections in a page. This happened:

1. I ordered them how I wanted them.
2. I updated the third section (without reordering it). When I hit the Update button on that section, everything looked fine.
3. I refreshed and it had moved to the first slot. This was also reflected on the front end. The changes were saved, but so was the unwanted reorder.

In another instance, I had 6 sections in a page. This happened:

1. I ordered them how I wanted.
2. I updated the sixth section (without reordering it). When I hit the Update button for that section, everything looked fine.
3. I refreshed the site and it had reordered itself to the second slot. The changes were saved, but so was the unwanted reorder.