When the splitter has 2 incoming belts and there is a mix of objects on the conveyors, then periodically the objects pass by filtration.

https://gyazo.com/6bf5130ad5012b7bc153a7f8fc5498a6

No, I'm wrong with 2 incoming belts, filtering does not work as such.

https://i.gyazo.com/7d28486361f88247a17cdcde98cc4fde.png

damn it, it seems that this is the last minor update factorio 0.17.52 broke the filtering:
https://i.gyazo.com/0b212195291ab2997baa137a3c7ec7c4.jpg
https://i.gyazo.com/1751f87598067e3cb1a920ce4158db87.png
but the last belts do now work at 270/s :D
https://i.gyazo.com/c46c77dbde8d225eac8d1461d3b2b9c2.jpg

Yeah, I'm having the splitter filters mess up my lines as well :(

270/s master race :D
I wonder when that was fixed to allow for higher speed belts.. I can't seem to find a changelog anywhere.

@Anon2k I've also updated your Belt Speed Tester by adding in a global on/off control 'Green', and variable time 'T' control in seconds. You can replace the Iron Plate with anything, I was just using that as my comparison subject.
https://pastebin.com/hr7hB9Dj

Someone should message the dev, because this is breaks all of my belt-based factories.

Apparently, it's not in the mod. I wrote to the developers: https://forums.factorio.com/viewtopic.php?f=7&t=73059&p=441047

I don’t know what to do anymore.

Oh noooooooooooooooooooooo

I do not know how much to wait for a response from the developers. I wrote a minimod that limits the speed of splitters to 120 / s. Check my bug-report with them, as soon as they fix it, you can disable this restriction.

https://mods.factorio.com/mod/SuppressSplitterSpeed

I'll check it out.

Kovarex has stated it will be fixed in the next update.
Hooray!

Yep, the error has been fixed.