Bug Fixes

• Ore exiting a cave can exit by any exit underground belt of that cave type (two different uranium caves

• Biters in caves spawned by rocks don't use main cave's evolution level.

• Belt dragging after a research upgrade (when replacing a belt with an upgraded tier by dragging) tries to fill the space between underground belts with regular belts still.

Design Suggestions and QoL Suggestion

• Bias the mixed resource patches towards iron, so it more closely matches the resource distribution.

• Make the intput and exit belts for the uranium cave not face the pipes that need to put fluid into them. Yes the can be rotated, but didn't realize this as first. So minor convenience change for others who never realize this.

• Pressing escape exits the regular menu, but not the coin spend/buy menu, kinda annoying to have to click out of it every time.

Hi senordingus,

First of all, I’m sorry for the delayed reply. I saw your report, worked through several of the items, and then mistakenly forgot to return to the thread. Thank you for taking the time to write such a clear and detailed report—it was genuinely helpful.

I checked all six points again again against the current build. Five of them have now been addressed:

• Resource Cave transfers are now isolated per cave record, and only one Uranium Cave expedition per force can be running at a time. Each cave maintains its own linked input/output pair, preventing ore from being routed through another Uranium Cave’s output. Existing legacy expeditions are preserved rather than forcibly deleted.
• Enemies spawned by mining rocks inside Resource Caves now use the Evolution value of the parent/main Cave surface.
• Newly generated mixed resource patches now use 35% Iron, 27% Copper, 25% Coal, and 13% Stone.
• On newly generated Iron, Copper, Coal, Uranium, and Underground Village entrances, the upper item and fluid connections now face toward the bottom of the screen, and the upper output endpoints have been moved farther from the cave entrance. Existing generated entrances remain unchanged to avoid breaking saves.
• The Coin spend/buy window can now be closed with Escape or E, as well as with its Close button.

The remaining issue is belt dragging after an Underground Belt Reach or belt-tier research upgrade. I have not fixed that one yet, so I don’t want to claim otherwise. It is still on my list.

Thank you again for the excellent feedback, and sorry that I left you without a reply for so long.

All good. Been enjoying the mod. I'll keep giving feedback as I have it! Thanks for the changes!

My intuition is also that the belt dragging bug seems the hardest to fix, just from what I've heard about belt dragging to be a very precarious part of the factorio codebase.

I have genuinely done everything I could to fix this. I checked every relevant part of the code I could find, searched extensively online, read discussions on Reddit, and went through the official Factorio forums and other available resources. After all that research and testing, I still haven’t found a reliable way to eliminate the bug completely.

The main lesson I’ve learned from this experience is that underground belt and underground pipe behavior is an extremely sensitive part of Factorio. It is not something that can be modified safely or casually. Once that behavior breaks, it can create unpredictable problems, and even after repeated attempts, the result may still not work correctly.

I have taken this as far as I currently can, but the bug is still present, and nothing I have tried has fully resolved it. I don’t want to pretend that it is fixed when it isn’t.

Based on my personal experience, I would strongly recommend avoiding changes to underground belt and underground pipe behavior unless there is a proven and reliable solution. I may eventually remove the underground belt and underground pipe upgrade research from the mod entirely, because keeping a feature that still has an unresolved bug may cause more trouble than it is worth.