This is on Win 10, version 14.22, no mods, on a 14.22-0 base map.
- Cargo wagons are fully-programmed. There's not a single unfiltered slot. Unfiltering a slot doesn't get anything un-stuck--it just loads from one of the working inserters.
- Twelve item types, with twelve inserters, with twelve chests. One item each. (Ignore the double in the top right corner in the screenshot--that one exception isn't helping or hurting.)
- Train track is straight, at least for the station and all the inserters; this isn't a problem with a bend or curve.
- Inserters are fast inserters, so there's nothing to filter; normal, filter, and stack inserters show the same behavior. Switching, rotating, and deleting/recreating the inserters does not help.
- Not all of the inserters/chests/items fail to fill. Some work, and some don't.
- The slots can be filled manually just fine. Filling and emptying the slot doesn't help.
- I have all stack bonuses, but this isn't a partial-stack problem seen elsewhere. The cargo wagons have entirely-empty slots waiting for items, but the inserters won't let go.
- Toggling between automatic and manual train control doesn't help anything.