i would wonder:
who did the previous work?
what do they recommend?
where are you located interms of your climate and humidity and drainage
etc are all important to a local architect's evaluation.
when was the house built, when was that repair done? what is the rate
of the problem advancing?
why monkey around at all for the reasons you mentioned?
how much money is available to play with this if it is a problem versus
a non-problem of support?
maybe leave it alone without further professional advice if this is
only a problem to you as new homeowner.
How does a wall sag? I've seen floors or ceilings sag, but never a
wall. Walls may buckle or collapse, but I don;'t think they sag.