I've been having some troubles with my rear wheel (Fiamme Hard Silver) going out-of-true after a single 50 mile ride. I've built several modern wheels before with no problems whatsoever, but for modern wheels I've always gone high tension (120+ Kgf).
I built the Fiamme Hard Silver at low spoke tension (~80 Kgf). Perhaps too low. Dunno. I read old tubulars like these can't handle high spoke tension.
I'm finding a single spoke will lose all tension (like the nipple comes unscrewed). I've always used grease on spoke threads and never had a problem with them coming loose like this.
Seems either I need to up the tension, try to get them more uniform, or apply some kind of lock-tite to the spoke threads instead of grease.