Great idea! I tried all combos, reproduced my original set of applets that were having issues, moved stuff around, reset panel, restarted and all but the issue would not get reproduced. However, as you suggested, installing applet, adding it to panel, uninstalling without removing from panel and then resetting the panel reproduces this part:
Random reordering has not happened yet, but I have hopes that it will show up with a few restarts and resets and moving around applets.
I also added some debug prints and recompiled/installed budgie-desktop and it seems positions of applets aren’t getting updated as evident (length says 14 but position of the last applet is 15 so the last two are not allowed to be moved down):
Don’t know how the panel saves and restores state when replaced etc, but I think there might be some problem there or in how cleaning up is done when an applet is removed via setting vs when it is removed because it was uninstalled. What do you think @fossfreedom?