hm yea could be, I had a error when i accidentally flooded my land. the game made a dirt dam to protect the rest of land from the water but made the dam over my items (bins and tent) as there was something under this new dam (my items) i could no longer dig or build there as "something" was in the way.
I warned the guide's (mihr) for this as it could potential destroy large areas of land unable to use it for anything ever.
Solution would seem to allow digging on spots that already have something on or under it but that could cause several other issue's (ppl removing sand under logs to make bridges being a" good" use of it..,but one can Imagen the abuse..)
seems your land area has the same type of "bug" ony created by the game and not man made like mine.