I have not had any issues with the harken blocks on either of my boats. I did have a problem one time using a plastic cleat on a spin halyard turning block where the line wore through the cleat quickly. Need metal cams in that scenario. I did have a ronstan series 20 block used as spin tack turning block blow up once... But that was an overload.
I have used some Garhauer blocks on my big boat. Seem very well built though maybe a little heavy. One double block I got had somewhat rough rotation though.

Karver blocks are too pricey. I have used a harken 29 mm carbo block for spin halyard block on the mast for several boats and never had a problem.