I got the blacksmith to upgrade the armor and it worked beautifully for a while, but since a recent update (the one before last I think), the armor is back to being heavy and the blacksmith won't upgrade it again.

Any thoughts?

Thanks.

You are right.
But then what was the point of getting the blacksmith to upgrade it? What changes has he made?

It's been a long time, but in case it helps someone...

In the current version the smith can upgrade Tilo's armor twice, after finishing two different missions for the Commander (he can also teach about the spider traps). The first update feels only slightly lighter, but after upgrading a second time Tilo moves noticeably faster and can even run a little (not jump though).