I guess it depends what your definition of "serious" is. This doesn't sound like it would ever affect me.
As far as I can tell, it will only cause problems if you don't delete entries from other tables that have a foreign key pointing to that row. There may be some cases where you need to do that, but generally isn't it better to properly delete all the rows from other tables that use that foreign key when you delete the primary key?
As far as I can tell, it will only cause problems if you don't delete entries from other tables that have a foreign key pointing to that row. There may be some cases where you need to do that, but generally isn't it better to properly delete all the rows from other tables that use that foreign key when you delete the primary key?