How did you fix it?
Does it every time Mark when the rebar is close to the surface. In one of those pics, the rebar was laid on top of the top tie rods and shifted to one side when they poured. Cracked the whole top of the wall.
That is why a lot of specifications called for rebar to be no less than 1-1/2" from the surface in most commercial application.
Now they have epoxy coated rebar that helps prevent some of that from occurring.
Look what rusting lintels can do to masonry.
Yeah rusting rebar and lintels, Mark. What a mess! 
I don’t think oxidation, which appears very minimal at best, is the underlying issue producing the horizontal cracks.
As well I have never seen were (3) rebars are bunched together for residential foundations, let alone so close to the outer surface of the foundation.
I made sure lattice or rebar frames were centered with form standoffs.
Thats poor workmanship.
Typically/Usually/Normally, when using bar steel drawings/plans are used.
Refer to a licensed foundation repair expert.
Just my 2 cents.
Just my thoughts, Marcel but a bond beam should have been used to span the opening. Not back to back angle iron spanning the opening. If you look closely the forward facing angle iron has a secondary plate steel positioned underneath for to increase deflection rigidity or to me it looks that way.
Yes there is a percentage oxidation that will affect the 'mortar bond ’ the CMU are staked on/bonded to but reinforced poured concrete is another medium all together.
Again. Poor workmanship. Engineers were not involved in planning.
Not disagreeing with you. Just my 2 cents, Marcel.
Best regards.
Robert