CG too far aft and out of the envelope.... Just a guess...
I dunno - the pitch seems to be the one thing that is pretty stable through most of the "flight" (or is that "fright?"). Rotation seems normal and smooth.
A textbook Dutch Roll - so a failed yaw damper? [nah, - never mind - Tu-154's anhedral supposedly eliminates need for YD)
Dutch roll - Wikipedia, the free encyclopedia
Anyway - stupendous work by the crew to work around the instability and bring 'er home!
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Edit: Chkalovsky Airport outside Moscow? (trying to translate the cyrillic)