Can old shock mounts be reattached?

Can old shock mounts be reattached?
Should shock mounts be replaced partially?

Definitely not! Read why...

NEVER! It is very dangerous! If they tear off again, and the shell tears off the frame suddenly, there is a high risk that someone will be injured! Also for Lounge Chairs, the risk of breaking the shell is very high! If one site tears off, and the other side is still attached, very often the shell breaks!
In the vast majority of cases, it is not the adhesive which tear off, but the dried out Shock Mount disintegrates. You can see it most clearly, when black rubber components of the Shock Mounts stick to the plywood or fiberglass side.
You should never glue the old Shock Mounts back on, as the next layer quickly comes off the old Shock Mount and it tears off again.

Sample of a shock mount with very dried out rubber

This side is usually glued to the plywood. As you can see the rubber is so much dried out that the shock mount is flaking asunder.

Should shock mounts be replaced partially?

Always all Shock Mounts should be replaced, as they are usually the same age, and if fresh, elastic Shock Mounts are mixed with old, dried ones, the old ones break even faster.

Please do not use cheap Polyurethane Shock Mounts!

Polyurethane cast rubber do not have the required elasticity and, in the long term, cause great damage to the plywood (lounge chair). Polyurethane cast rubber is not vulcanized, the 2-component material does not combine correctly with the metal insert!
– The shock mount on the left shows the bare metal. All we did is a cut with a cutter blade.
– The middle shows an old shock mount, insert was cleaned with a machine wire brush.
– The right shows in the middle a correct vulcanized insert. It was much effort to get the neoprene off. Below a un-vulcanized correct insert.