I bought some psp #555 white ones to try in AFM.

Couple of questions -

The ones that actually worked were good, but there were two duds out of six, so I was wondering if they are prone to manufacturing issues? I'll take those four out as the area needs six, but they were quite effective. However, if they have a high fail rate/defect rate, I'm concerned.

If I got two out of six dead on arrival I'd be seeking replacements. I bought about 150 with none dead on arrival. At about a dollar each they aren't cheap for what they are. As a solid state device they should have no problems and once installed the failure rate should be incredibly, almost to the point of imeasurably low.

I find the type 44's I've been using a bit tough to install in some sockets - the tip to side pin distance is pretty tight.  It is possible to rotate the LED part within the 44 base if you are not careful and you don't want to do this.  I remove the socket from the playfiled, give it a quick clean and if necessary adjust the socket a bit with needle nosed pliers.  I also rotate them by gripping and moving the metal part of the base.