BNC input sockets break away from the mainboard PCB. They are not overly robust so be gentle with them.
Checked. Indeed, I've see other users doing different kind of operations to make theses BNCs a bit more solid.
On my scope, CH1 BNC was slightly loose, I simply re-soldered the joints with brand new solder. And while I was there, I also re-soldered BNCs for CH2 and TRIG.
There also was a factory recall for these scopes as early units could blow the ground trace between mains ground and the input BNC shells. Check there's conductivity between mains ground and the input shells. It's a safety issue.
If you check the Tek website there's a list of the SN#'s affected and if your unit has been fixed after the recall.
Sadly, one of the previous owner removed the Tektro tag from the back of the unit, where the SN was stamped.
As far as I understood, there's been a safety continuity from each BNC to earth on each and every single TDS 2x0 scope. But the problem from the earlier models was that this connection was ensured by a tiny track on the PCB that could easily get destroyed after a first misuse of the scope. And indeed, the BNC could then become a hazard in this case.
As far as I understood from a video I saw on Youtube about this issue (*), the "new" models have a metal tab added on the PCB. This little tab would create a contact from the big track on the PCB (where all BNCs are connected) up to the screen chassis, and then back to main earth.
I tested continuity from BNCs to main earth on my scope: all good!
(*)