I would say that if your original sheer pin broke after 1.5yrs of use and then you broke 3 in a short period of time with the replacement gr2 I would stick a gr5 in it.
Are you sure there suposto be a gr2? Gr2 is piss poor chinese quality bolts. You can hardly get them tight with out stretching it.
Are you sure there suposto be a gr2? Gr2 is piss poor chinese quality bolts. You can hardly get them tight with out stretching it.