GeezyRider 

I've been down the vintage Raleigh 71mm 23 tpi bottom bracket shell road myself. I tried the 68mm Sunlite threadless universal bottom bracket but that 3mm made a big difference. I didn't feel that the non-drive side of the bottom bracket grabbed enough threads to be secure. Perhaps this is why yours keeps coming loose. I ended up polishing the minor pitting out of the original cups and found a square taper spindle that gave me a good chainline. It's been performing beautifully.