Differences with 2 Chronicles 21:2

[Christina]

different scribes copied different scrolls.

Yes, this is the logical or likely explanation.

handwriting differs from individual to individual

In this particular error I believe it's deliberate - at least a change from the Vorlage to the revised text for the new Masoretic. A scribe can't easily mistake the word "Judah" for "Israel" unless maybe he has cataracts. The Aramaic and Lxx likely was using the pre-Masoretic text.

Israel ??????????

Judah ???????????

That certainly gives one something to think about. I always prefer to give the benefit of the doubt, but deliberate tampering cannot be ruled out, though I can't think what would be the motivation behind this particular case. Places where deliberate tampering is obvious in the Masoretic text is the passages concerning the Messianic prophecies (eg: Isaiah 53) and the almah/virgin issue. Deliberate tamping can be found in the Greek NT too, sometimes obvious and sometimes subtle.