I don't normally do merges as part of db_errors, just the lines I'm related to, just to put it into context. If I have or will propose merge based on db-errors, I most likely will leave it for PM/TL to complete.
Anyway, one problem I see is that members here have wrong parents attached and that is used as an excuse to reject or unmerge match, rather than correct the parents. It's also very common for profiles to have other data that represents multiple real people (and the PMs will not correct) to the extent there's often no way to discern who the profile is meant to represent.
I have a few profiles I don't want to see merged because the other PMs won't make any changes. I've added notes to at least some of these warning against merging, but I'm not sure that others who come along will honor that.