Upon thinking deeper into your Technics problem, I'm assuming this was a used 1200? It's possible the previous owner tried taking the tonearm apart for whatever reason and lost one (or more) of the tiny bearings. If this is the case then I could definitely see something like this behavior happening with the tonearm so a bearing replacement may be a wise decision.
From the video, it looks to be an original Technics headshell, so I don't think that's where the problem lies here.
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