When I try, it gets stuck in an endless loop of hacking away at the vein. I try to back away and go at it again, nothing. I leave the mine and enter again, nothing. I tried a new save. Nothing. I tried verifying files through steam, running without mods, starting a new game without mods. Nothing works. Not even swinging away manually. What's worse is that it was working fine two days ago and now I get this. Anyone know what's going on?

After disabling all your mods, have you tried mining ore veins from a different place ???

ALSO:

You can equip your pickaxe and manually attack the vein, and it should count as mining the ore and add it to your inventory every three hits. -> It that working for you ???

How are you disabling your mods exactly? Are you using NMM? Have you disabled any SKSE stuff?

This happens with all veins?