Not sure what caused it but started noticing loaders all around my base that were whitelisted for a single item were suddenly set to split lanes with 1 filter after large scale bot upgrade commands. Will see if I can reproduce but wanted to note it here in case you know of a potential cause, or know of a reason this might happen. Very painful to go fix lol.

Was this using a default upgrade planner, or one you set up with specific upgrades?
What version of the mod are you using?
Do you have any other mods installed?

So far I can't reproduce it, so no worries if haven't heard it reported, will keep an eye out for any potential causes.

It was one of those things i noticed in retrospect.

Understood. Off the top of my head I can think of two possibilities.

1. When I initially released split-lanes there were some instances of the loader swapping modes on upgrade in general - fixed that one early on. Using a default upgrade planner, or just fast replacing a loader, now keeps the split-lane state of the replaced loader.
2. If you create a custom upgrade planer and specify loader tiers to upgrade from and to, there are two icons of each loader shown. One is a split-lane version while the other is the non-split-lane version. The icons were the same, so it was too easy to set it up to upgrade a split-lane loader to another tier of non-split-lane loader. This was improved with a new icon badge to indicate the split-lane version of the loader.

If you are able to reproduce this and it is something OTHER than the two above, please let me know.

Yeah it may be related to #2, not sure I understood the reason for those different icons so I could totally see me using the wrong one as possible.