In advance, the answer is:
We actually don't know. The general assumption, however (based upon how he reacted to past issues with the armor), is yes."
In the later half of Avengers: Age of Ultron, Ultron never appears to use the magnetic attack for a second-go-round. With this in mind, and the fact that Tony Stark appears to use similar armor (sets) throughout the film (exception being the Hulk-Buster AddOn - not a fullOn separate armor), it appears as though one of two situations occurred - Either:
- Stark never got the chance to fix the issue, and Ultron simply never used the magnetic attack against IronMan again
- Stark did fix the problem, and Ultron never successfully used the magnetic attack again (against IronMan) during the film
Let us set up some context.
Ultron was originally an foriegn artificial intelligence (A.I.) that was trapped in the gem of Loki's scepter. This A.I. was used by Bruce Banner and Tony Stark in something known as the "Ultron" global defense program. When they initiated his (Ultron's) systems, his first act was attempting to destroy J.A.R.V.I.S. - which he nearly succeeded in doing. Seeing that Ultron was also able to access technical systems internationally, crack into the world wide web, and even process monetary transactions involving money he didn't own (how did he pay for the vibranium?), it must be noted that he also may have been able to access the IronMan's systems as well.
More on Ultron's technical capabilities and IronMan's security depth here:
Why wasn't Iron Man's armor a weak point in Age of Ultron?
With this clarified, I now introduce a theoretical statement, which will act as the ground of my reasoning:
Ultron was a pragmatist, and did not waste time or energy on anything that wouldn't have pushed his agenda/world-ending plot
In this case, two situations (as mentioned earlier) arise - Either:
- Ultron had no further use for this magnetic weapon, which is why it never appears to be used again in the movie spotlight
- Ultron (was able to) scan IronMan's armor, and detected that the vulnerability no longer existed, nullifying the use of this weapon for the rest of the movie
In the first case, it would not have mattered whether or not Stark had fixed the issue - Ultron never uses the magnetic weapon again, and therefore, the fix is little more than dead-weight on the IronMan. In the second situation, IronMan's (theoretical - not confirmed) proactive thinking keeps him from getting his NicTol hide handed to him in a second round. In addition to this, I also introduce one final note:
(specifically, the section labeled "Powers and Abilities")
This may change things, seeing that the attacks Ultron was using may have been gravity-based, and not magnetically-based. In this case, it appears as though Ultron simply chose not to use that type of attack against Stark later in the movie. This leaves us with an absence of important data that would have gone into further analysis. So, to answer the question of:
"Did this include some sort of solution to the magnetism weakness? If so, how?"
We actually don't know. The general assumption, however (based upon how he reacted to past issues with the armor), is yes.