This is an irregular crash, it doesn't happen 100% of the time, but is more likely to happen the quicker you're moving, with it happening more than 50% of the time if the player is running at full speed and holding down the right mouse button to mine items in sequence. The loader must have been in the "correct" direction, i.e. in input mode, not output. The loaders are a copy of vanilla loaders but altered to be 1x1 tiles, the only substantive changes are to collision box, collision mask, selection box, belt length, belt distance and container distance. Can't reproduce it with vanilla loaders. Can't reproduce it when the arrangement is blueprinted and then rotated by 90, 180, 270. It seems like the splitter hasn't had time to do something crucial (Splitter::disconnectGroundConnections?) if the entities are removed at maximum speed. If you remove each item individually without running and wait between each item removal, the game doesn't crash.
To reproduce: hold down right mouse button just above the loader; start running south; mine the loader; mine the splitter. Problem behaviour: game crashes more than half the time. Expected behaviour: game doesn't crash.
Crash log below, example save attached with a copy of the loader mod.
Crash log