[2.0.55] Transport line gap opens up in middle of belt where it shouldn't

[SNACKaJACK]

on the blue belt carrying blue science on the right of the clip, a transport line gap opens up after the corner in the belt. The supplying belt is backed up so a transport line gap should not open up. Below I have attached a video of the issue, my save and the logs.

2025-06-30 17-10-27.mp4

(58.44 MiB) Downloaded 27 times

To infinity and beyond.zip

(43.81 MiB) Downloaded 23 times

factorio-current.log

(8.18 KiB) Downloaded 15 times

[eugenekay]

Whether this is a Bug or just a side-effect of Sideloading is up to interpretation.

Corner belts do not hold the same number of Items on them as Straight belts - the "inside Corner" is smaller, and the "Outside Corner" is bigger. Sideloading of Belts tries to use the "Upstream" Transport line, then the "Downstream" one (which is slightly blocked/backed-up while waiting). So if the Upstream/Outside line is empty; then and only then is the Downstream/Inside line able to move: but because its an Inside corner only 1 Item was able to move Forward until there is a big enough Gap for more Items to enter the Inside Corner... and then the Gap goes away.

Ugly Solution: add an extra piece of Straight Belt before the Sideload occurs. Or re-balance more Blue science packs onto the Upstream/Outside lane.

[SNACKaJACK]

I don't think that's what's happening here, if you look closely at the clip you can see that the gap does not form at the point where the blue science belt loads its items onto the mixed belt, but instead it happens 2 tiles further. It looks like the gap starts in the middle of the mixed belt on the straight belt after the corner of the mixed belt, not in the corner of the blue science belt. I personally think it might have to do with the splitter further down the line as well.

[ndh]

Looking at the video can be misleading. Should be looked at in game, stepping through frame by frame.

[Osmo]

Possibly related/a duplicate of 129429

[Rseding91]

Thanks for the report however we won't be doing anything about this. The splitter you've placed inline, and the fact you're side-loading means the recursive "update the one in front of me first, so then I can move forward without leaving gaps" breaks down here.