I found 2 isotopes in Wolfram database which are marked as unstable, but their lifetime is indicated as infinite (germanium-76 and selenium-82). The following chunck of code illustrates the issue:

g1 = Table[{{z, a} ,
IsotopeData[{z, a},
"BindingEnergy"],
IsotopeData[{z, a}, "Stable"], 
IsotopeData[{z, a}, "Lifetime"],
IsotopeData[{z, a},
"FullSymbol"], 
IsotopeData[{z, a}, "Name"] }, {z, 1, 118}, 
{a,  IsotopeData[#, "MassNumber"] & /@ IsotopeData[z]}] //
Flatten[#, 1] &; g1 // Length

Select[g1, #1[[1]] == {32, 76} &] Select[g1, #1[[1]] == {34, 82} &]

Is it an error of what?

Attachments:

Untitled-10.nb