I'm not familiar with Mandelbaum, but the online Dante using his translation looks generally nicely done.

Even in college, I never read much of the Purgatorio, only the Inferno, so you may well already know more about it than I do. If you really care enough to, say, go to a university library, you might find other translations just to compare. In English, Dorothy L. Sayers (the British mystery writer) and John Ciardi (the American poet) might still be worth a look despite their age; more modern ones that look interesting include Hollander and Kirkpatrick.

So, you probably also noticed this, but in the Italian, the point seems to depend on repeating the verb 'uscire' in a play on words: the hymn issued from his mouth so beautifully that, the poet says, it made me 'issue' from my own mind, so to speak. Mandelbaum, rightly recognizing that that's unlikely to work in translation, seems to have opted to signal the existence of the pun by changing it to a play on the word 'move,' which may be equally vague, just a gesture in the general direction of (my guess) being somehow outside oneself. That seems reasonable enough, though as with any translation of a poem in rhyme and meter, other options are undoubtedly possible.

My Italian is only up to opera librettos (and then only with a dictionary or an English translation at hand), so you might want to just ask in the LEO It-De forum what their associations are with the verb, or what their footnotes say, since no doubt the Italians all had to study it.

Or maybe someone else will have another translation, into whichever language, on their shelf. I'm sorry I can't offer to check, as most of my books are in boxes.