New Stand config brings about new TT problems

I recently bought a new plasma TV to help make my shared Living Room/listening room look more presentable. Prior to this we had a 55" big screen TV with the 5 shelf stand to the right side of the TV
Now the stand is lower and the big box TV is gone and the plasma hung on the wall. However I am getting a lot of noise when tapping on the TT plinth. This was not the case prior to this new config. I am assuming that the problem is sonic feedback and that the old big screen TV was helping to shield the TT from most of the feedback problem. However, if correct I'm not sure what to do about it short of a dust cover. And maybe that is the answer. The new config picys are shown in my system here, while the old config is shown

FWIW, I am using a sand box now as before. In an effort to figure out this problem, I've removed the 3" maple shelf shown in the pictures and gone back to the 1" maple with separate motor platform. I've also changed the mini TNT feet back to the stock feet. There seems to have been little or no change
So therefore I'm still assuming sonic feedback. Suggestions, insights, etc will be appreciated.
It is unclear to me if you are using the same table for the VPI as before. If so, and have moved the table, perhaps the table is now resting on a less solid area of the floor. If you are using a different table, you need a more solid one. I suspect that the old TV also was heavy and weighed down the table in the old setup. All VPI's need solid footing...the more solid, the better (except for the motor assembly on the rim drive). Yes, sandbox's, maple platforms, etc. can add to stability, but there is nothing like a solid table on a solid floor for your turntable.
Thanks Stringreen. It is the same table. You may be on to something since I am now also getting some footfall problems as well. Prior to the move I could jump up and down right in front of the TT without any consequence. Now I can hear speaker noise when I do so. No skipping but noise. I have planned to go under the floor and add extra bracing. I did that with the prior config but since the moving of the TT there may be no bracing directly under the TT as before. thanks
Stringreen. I misunderstood your prior post and your question about if it was the same table (stand). That stand is the same stand as before which is a VTL. They are stackable component shelves. There are 3 on the left and 2 on the right. Each component shelf is spiked & each tube is filled with sand as well. The down side is that the shelving MDF sits directly on the frame. I've thought about making some maple shelves with spikes for it but haven't had chance yet.
>>there is nothing like a solid table on a solid floor for your turntable<<

Actually that's not true.

Depending on the particular situation, a wall mount or ceiling mount can isolate the turntable better.

Every situation, including the table itself, is different.
I would be much more willing to put a Linn on the wall than a VPI.
Back in the party days of the 70's I used to suspend my TT from the ceiling. It saved a lot of good records. No problems with footfalls, parties, nuclear explosions, etc. OK I exaggerated about the nuclear explosions
I think that you are correct about the bracing.
AudioFeil. I have been thinking about that for my Sota Cosmos TT. It currently sits atop a Sistrum platform (3 pillars design) but my floor is not rock solid like concrete floors would be. It's your typical plywood floor that "flexes" when you walk. Indeed, i suspect that wall mounts would be best for all but the heaviest TT's.
Target use to make a good wallmount at a decent price. I heard about Mana as well which Art Dudley had used for years under his Linn. Not sure what he uses now. Who makes good TT wallmounts nowadays???

Finite Element

The Finite Element wall mount is quite pricey, about $2K if I remember.