I have a two-socket fluorescent lamp. Initially only one light tube was inserted and it worked fine. At some point, it started to go off seconds after being turned on. I thought the tube went bad, so I bought another F15T8. Surprisingly, if inserted alone, the new light tube would also go off right after being turned on. However, if I put both tubes in, BOTH would stay lit. The OFF switch then gets very hot (>100 C), which did not happen when I was able to use just a single tube. The lamp has two switches. The ON switch has to be kept pressed down for a few seconds until the light is turned on, while the OFF switch only needs to be pressed briefly.
How should I understand what happened here? Is the switch going bad and did that cause my first problem that a single light tube no longer stays lit? How could the switch get so hot?