standing rigging

[Killick69]

Noticed back stay on Night Cap has a broken strand. How serious is this? Wire is rusty in places and this applies to the other rigging also. Where is the rigging most likely to fail......attachment point to mast, wire, turnbuckles, swage points or chainplates? I checked a few of the chainplates and would appreciate your input. They appear to all (or mostly) be u-bolts and the ones I checked were dirty and rusty, which makes me think, clean and refit or replace. Are TH chainplates a problem area, Are these standard size s/s u-bolts and hopefully not too expensive. My thinking is to sort out the chain plates myself and then get standing rigging replaced.
Has anyone replaced/cleaned, checked and refitted chainplates. I would imagine it would be possible to remove chainplates one at a time and clean/replace/refit, without the mast ending up horizontal.

Thanks, john