Code question

HI, This is my first post here so Hi to everyone. My main skills are machinist/welder/mechanic but I am not so good with electrical issues. I am working on a 24 bulb tanning bed where 2 bulbs will not light. They were all working and then the bed was moved in the back of a pickup and some of the lamp holders on the top section broke where they clip to the top and so I replaced all of them. Now two of the bulbs will not light. I have tried swapping bulbs, starters, ballasts, even the bulb holders and still the same two will not come on. I scrapped the wires where they fit into the holders to make sure they were making contact. They do show some light on the ends but do not come on completely. I have checked continuity from the ballast to the light holder and from one holder to the other and the ground and all that checks out. This completely stumps me. Anyone have any idea what else to check? TIA

A rental house I own had an old American Electric pull-out fuse sitting outside the electrical panel. It was for the hot water heater and I had it unplugged cause the unit was vacant and water was shut off. Cleaning service threw it away cause they thought it was garbage! This panel was installed when the house was built in the 50's. Anybody know a source (but not ebay) to buy these plugs? Thanks!