more pics.

what can I do to fix this?

It doesn't really look like sunburn, does the plant have leaves? Is it rooted or are you trying to root it? Can you take a picture of the whole plant and show the tips too? Spider mites would not do this but if you have them they show signs on the tips mostly.

The trunk looks shriveled in the 2nd photo - is it soft there or still pretty firm?

You could try wiping the branches down with a little hydrogen peroxide and see if that takes it off - it could just be lichens or something topical.

I don't see sunburn either. The tips loosing a few claws during rooting should be expected. if its rooting still (at least that's what I understood) I would recommend not moving it around so much and using a small container next time. find a warm part sun spot and then forget about it until it has leaves. Good luck with it.

Moving a cutting around while trying to root it results in breakage of the very fine roots that are forming and will result in your cutting not forming roots. Put the pot in a warm spot and leave it there. If rot hasn't set in, it will eventually root.

Okay thanks