I'm noticing that peers using the (new?) release of uTorrent 3.4 are all being blocked with the message "Ignored: bad data".

Is this a problem with uTorrent, or a problem with Tixati not liking the traffic this new version is sending? There's a bug somewhere...

When it says "Ignore" the reason shows in the Status. Could be metadata, sending data, bad ACK, etc.
You are seeing faked peers in that instance. Since old old old version uTorrent encodes micro symbol. If you right click on a peer, Copy all client data you can paste the 20 byte character peerid. It would likely say something else other than "utorrent 3.4" which was negotiated from extension protocol.

uTorrent 3.4 usually is the android version of µTorrent - so no fake iirc.

"Ignored: bad data" could mean many reasons, one of them might be a hash-fail on an mp3-file. I have seen µTorrent downloading 1GB for just 250MB of mp3-files, just because there were peers that did some hash-fails with the pieces. In that particular case, Tixati ignores those peers for sending "bad data". My 5 cents.

I have noticed this also. Not with 3.4 but 3.4.8 specifically. It is common with Vuse 5.0 but never had a problem with any uT(except for ones that are constantly ignored) until I switched to Tix 2.43. It does seem to be a glitch because if you un-ignore the peer, they don't seem to get ignored again.

This is likely an attack on the swarm/INFOHASH
There will continue to be attacks on any swarm, whether it's peer injection, connection clogging, DHT poisoning, IP harvesting, false announces...

What's annoying for my client, I can routinely see on a rare file, up to 1 MB (20x the INFO dictionary) sent protocol with no data. When you catch the Peers tab/info... they show as unknown client (peerid is mostly ___ or junk)... 0% of the file, and immediately disconnect once they connect to you for the metadata transfer.
What is annoying on the other side.. there are many clients which still do not support metadata transfer from magnet: