Old Linn Sondek with SME 3009?

Nice plinth! Can you gently tap the record, just moving the suspension whilst it is playing, without it jumping? From your video, the suspension certainly isn't tight.

 

Unfortunately, I sold the table a few years ago.

 

it's all right and I agree!
Tomorrow I hope to know the price
If the price is right I will buy the deck!
Now I see the absurd prices of the turntables
I don't buy if the price is high due to this trend.
LP12 and SME 3009 is today unattractive by Linn Fans (maybe)
and this (in theory) means lower price (I hope)

 

Ok, you can't check that then!

You can set up a LP12, so you can repeatedly bounce the suspension whilst it is playing so that the platter almost touches the top plate and it will not jump. Nice party trick, but all you are doing is showing the suspension is working as a piston and not skewing.

Unfortunately, if you have a really extra bouncy floor and it unsettles the suspension off-centre, then you could end up with the problems you faced. As @Pastafarian mentioned, you may be able to sink screws and stop the problem, but occasionally even this isn't enough.

 

Occasionally I look on eBay at the prices of vintage Hi-Fi and am often staggered at the prices of some items. With the interest in vinyl replay many turntables, arms and cartridges are going for silly money. I have seen some moving coil cartridges being offered for more than they sold for 30 years ago and the suspension on them would have degraded considerably 20 years ago! There are also many products that were considered fairly average being bought for good money.

Against that new prices have also gone up way above inflation in the last few years, so bargains can be had - hopefully you have found one.