Salem

After flattening the ground on a few tiles my stats start decreasing at a steady rate, even after I stopped digging. This caused me to get knocked unconscious thee times in a row without me even being able to move before it finally stopped. Not sure if this is normal, or possibly related to the terrain?

Are you in the darkness or were you perhaps bitten by a snake?

Nope, neither of those. I thought status effects like poison were supposed to be removed when knocked out.

Did you have crime debuff?

Do the stats decrease in their total amount, or in their "effective value"?

That does sound like the darkness effect (you hit drain before you hit the darkness warning I believe). However, you shouldn't have been able to ever recover from it if it were darkness.

Puzzling.

I haven't even started on crime related activities. I'll describe the situation in more detail:

I was flattening terrain, dropped some of the dirt and because my phlegm was low I wandered back to one of my baskets to fetch some food. I was knocked out before I managed to reach the basket however. A few moments later I teleported to my homestead which is just a few meters from the basket and when I tried to get walk too the container I was knocked out again. After the next teleport I couldn't even take two steps before I was flat on the ground. I've been in that area for about two days and it's the first time this happened. The only way I managed to get out of the issue was to teleport to Bosten right after my character got up. I scavenged for some food before teleporting back to my homestead and my stats have since recovered.

Did you have some movement type active? Wander mayber? or foraging? Do you also get knocked while standing still?

I think you are just barely inside the darkness...and once you lowered your phlegm from digging to below the drain threshold you didnt notice and it was too late. You can test it by standing at your leanto and spamming attack moves to use up your YB. If you are in the darkness, you notice a steady drain after the YB drops below a certain amount.