Hmm I've yet to have a problem with RS on standalone fixtures, are you using grounded cords for them? I know RS lights are hard to start if the light isn't grounded.
I know don conveated a RS strip in 2ft to preheat with the same ballast..it could startup without the starter but was hard on the lamp and started slowly...but had an interesting rapid start/semi preheat startup with the starter installed
Hmm I once saw a light in the bathroom at someone's house that would glow dimly before the (very slow) starter fired. The lamp was doing that dim-flicker-glow thing like an EOL lamp on a F40T12 two lamp HPF rapid start ballast...
Yeah same thing at my grandpa's shop. There's one troffer that had dead lamps in it for who knows how long. They were super blackened 34W GEs (black etches so they're not too old, but they could have been dead for years). I relamped them and the ballast takes literally a MINUTE to turn on the lamps! And this is rapid start. They don't start too rapidly lol. I've actually noticed some preheat set-ups instant start, which is faster than RS which makes the name "rapid" deceiving lol.
Really old/heavily used rapid start ballasts seem to do that really slow start up i am not sure what causes it but usually i just replace them at that point! Btw what lamps were you using?
I have an F40 single-lamp preheat fixture (it was rapid start but I converted it) and it almost always glows dimly immediately upon switch-on, before the starter kicks in. If I disconnect the ground it is less likely to do that.