Should probably be a way to undo upgrades. Out of curiosity I cut short days in and maxed everything and it's been multiple days without being able to hit the bottom. Think the offender is the increased resources in the ground. Have reached the layer above the bottom with 1 of the 22 workers once post coffee use (should really be able to buy 1 coffee per max worker) and not at all close since then.
The rng on how far they get down pre coffee use is a big range furthest I've gotten down before coffee is about 160 and shortest is 106.