Video needs to be uploaded to the likes of You Tube/Vimeo etc and a link to it posted here. Marek's vaccine does not give 100% protection.
The "paralysis" is usually asymmetric with Marek's but there is such a huge variation with the disease from something as innocuous as a droopy eyelid to floundering on their side in the splits, with everything in between, that nothing is set in stone. I have certainly seen the posture your bird is exhibiting in Marek's birds. The type of "paralysis" can also vary from an inability to "feel" or control a muscle, giving rise to a drunken type of demeanour to a more rigid, spasm of the muscle. It may be that the lack of sensory feedback from a limb causes them to tense perhaps as a panic response, but they may still have the ability to move that limb when stimulated.