On old larger boats (with cabins), there will be delamination on decks but I'm not familiar with the construction of a Sunfish. And the soft spot here is on the hull, not top.Are they solid glass?
I've seen it written here that loose Styrofoam logs are the result of bad trailers. That, combined with dampness compromising the yellow "glue" is a formula certain to loosen Sunfish blocks.For recreational use, loose blocks don't make a difference. The boat will make some bad noises when hitting chop, but the boat will not fall apart or spring a leak as a result. Tons of old Sunfish out there with loose blocks (wouldn't be surprised if it is the majority) and they sail on with most sailors none the wiser. You wouldn't want to race it, but to sail and enjoy it will be fine.
Wow! Those blocks took a hit!
My objection to great stuff comes from a competitive place and I am willing to spend a bit more for light weight, longevity and stiffness. We are on these boats for about 26 or so events a year in 3 seasons for racing and it's nice to have confidence in the equipment.