How about Ezzy's pulley?

www.ezzy.com/accessories/sail-pulley/

Ah yes, been there: not only the welded ones.
Some brands use a nice inox pulley but topside is fastened with a bolt that is not very seawater resistant.
Somewhat hidden within the sail webbing (and within the top axle), it is worth a check for heavy corrosion.
Ran thru a quiver once and had to replace 2/3, totally rotten, sliver holding it together.
Ezzy pulley=one of the very best

yeah Pete, had the same thing happened to me a few years ago, ezzy pulley replacement worked a treat. I keep a spare in my Bucket 'o' things.