Ortofon Concorde Mix MKII Twin

Bought these because it's getting harder to get replacement styli for my old Concordes. I like my old Concordes better but these sound ok. However, not long after I bought them, I was playing out – the box is nice for bringing them along – but during the night the needle fell of one of the styli. I didn't think much of it that night and weird accidents happen, but the other day the needle fell of the other stylus.
I actually never tried needles just falling off a stylus before and I have been using Ortofon styli for more than 20 years and played quite a bit ... seems like MKII styli have really poor build quality!