Navtech 500 Turnbuckle stuck

[zachduckworth]

Post title says most of it.

My boat has some Navtech series 500 turnbuckles, the kind with the nut in the middle. They are mostñy hard to adjust and one is frozen unless I put a torch on it. The adjustment nut on that one is a little loose as well. I am planning to replace them all with open body Hayne turnbuckles this year but I was just thinking it might make sense to replace the frozen one now. Is a loose center adjustment nut on those a danger that could result in failure? Not the greatest product..