isomat stemball tangs

[woogie]

Has anyone seen or heard of an Isomat stemball tang that was assembled properly fail.? i.e. the stainless steel stemball on the end of the wire pulled through the aluminum seat in the spreader base or the mast head.

[Brion Toss]

Hello,
What you are describing is possible, a couple of ways. Most likely, a cup washer was needed to fill out the space between the seat and the stemball head. Some wire diameters don't require that washer, as the heads are big enough to fit the seats. But if the washer is needed, and missing, there's not quite enough grip on the seat.
It is also possible for the seat itself to fail. If this was the case, even a cursory inspection will reveal it.
Note that, regardless of the cause, it were a good idea to check on proper wire size before rerigging.
Fair leads,
Brion Toss