LTN troubleshooting

[zOldBulldog]

Hoping that someone can give me hints for how to troubleshoot the following. Or maybe there is an obvious mistake that you can mention.

I have a simple setup (or supposed to be):
- Stations always load and empty a full train.
- I leave 1/4 of each chest/storage empty as a safety but still leave enough content so that it doesn't run out while the train is on the way.
- I use full balancers (Raynquist 4x4L) and chests/storage are indeed staying almost identical in content.
- I do NOT try to make my stations unload at max speed. By having extra capacity I tend to use them as a material buffer to ensure constant availability.

But I occasionally catch a train at the depot that still has content. I am under the impression that it happens due to an extra train being sent causing it to bring the unloader over capacity. I have a nasty suspicion that this might be happening when I add a station from blueprint or copy/paste.

These are my capacities and combinator settings:

STORAGE CAPACITY
================
loader: 320 stacks = 16kx4= 64k ore, 32kx4=128k plates, 64kx4=256k circuits
unloader: 320 stacks = 16kx4= 64k ore, 32kx4=128k plates, 64kx4=256k circuits
wagon: 40 stacks = 2kx4= 8k ore, 4kx4= 16k plates, 8kx4= 32k circuits
(1-4 train)

Depot
- isDepot
- circuitID = 1
- minLen = 5
- maxLen = 5

Provider
- Provide Stack threshold = 160
- circuitID = 1
- minLen = 5
- maxLen = 5
- trains = 1

Requester
- Request Stack threshold = 160
- Provide Stack threshold = 1M
- Material = -48k ore, -96k plates, 192k circuits (always leaving 1/4 of station empty)
- circuitID = 1
- minLen = 5
- maxLen = 5
- trains = 1