Two years in a row now! What is doing this!

[Bear78]

Moles eat worms. Nothing much else. If they do anything to plants it is generally underground, digging through the roots. We had a lot of mole problems in our last garden and have to say that we never found a plant damaged above ground by them.
Wish I could help, but no ideas,sorry.
Yes the stem could be taken as a cutting.

Thanks! Well both pepper plants were actually cut right at the roots now that I’ve looked at it more. Not really above the ground by the looks of it so I guess it could be a mole?

 

[Oliver Buckle]

Provided that what Americans call a mole and what we call a mole is the same animal , no , not a mole. That you have found mole tunnels elsewhere doesn't seem important, they are carnivores, and if there is no tunnel at the plant it could equally be any rodent. I don't know what ones you have there, but some will be carnivores, some omnivores, some vegi, those same ecological gaps get filled everywhere.
Again, I don't know what species you have, but from the description of the damage I would think some sort of cut worm , a larva that travels in the soil just below the surface, would be the most likely explanation, but it must be getting hungry if you haven't noticed it anywhere else
Nasty neighbour?
Bloody kids with their ball?
Dunno, sorry.

How about opening a can both ends with a tin opener and sliding it down over the plant, then 'Screwing' it down into the soil a bit? Not so much you cut the roots yourself
I sometimes use large plastic bottles with the base cut off in the same way to protect young plants in early Spring. If the ground is friable it will go in 1/2" and hold fairly well.