A friend of mine had issues when updating to this latest tox. What we had to do was load his tox profile in utox, then close utox and then load that tox profile in miranda. That fixed the problem; otherwise miranda was saying (in netlog) "unable to load tox profile".
Additionally, multiple filetransfer at once resulted in mismatching md5 checksums; I'm now replicating the issue.
EDIT: Testing transfers shows that even to uTox, the transfer is terminated/cancelled midway (at seemingly random points).
EDIT2: Seems to be a tox issue as this happens with uTox->uTox transfer as well. The difference is however that uTox resumes from where it left off whereas Miranda gives up.
The updated toxcore however helps as my friend was previously unable to use the updated toxcore and stay online - and now he can!