Shameless plug...
So, there seem to be 2 types of these anchor problems. There are the:
"Someone doned something wrong when writing their addon." errors which are bad.
And there is the:
"For some reason after you have a certain number of addons, the game just throws this error at you but everything continues working fine." errors.
I can't claim to understand the latter one, but I do have a way to make it less annoying.
In comes
Zolan's Anchors Away. It is kind of like cold medicine. It doesn't really fix the problem, it just kind of makes the symptoms go away for a bit. All it does is suppress that one specific error.
It does not fix the problem or explain the problem and it even could suppress a real problem. By default it still notifies you in chat if the error happens, but it is better than pulling up a window every time you log in.
Zolan... Bringing you cheap fixes for crappy problems since 2014.
Hope this helps until someone smarter than myself figures out what is going on.
~Zolan