it appears as $oid when I copy it from my document itself. But what I sent was the result of my findOne() and in this case it appears like that.
department an category were working. I didn’t need to add _id for it to work. In fact, when I tried it with them, it stopped working.
As for color and size, it didn’t work this way either.
EDIT: I removed all versionKeys from my models, still didn’t work.