Why does the fluorescent lamp flash

This question depends on how it flashes. Based on principle of its function, every fluorescent lamp flashes. Without electrical ballast twice the mains frequency, i.e. 100x per second. With the ballast then normally in tens of kHz, i.e. 10000x per second. During slow flashing, the human eye detects flickering only in the form of a so-called stroboscopic phenomenon.

If the fluorescent lamp flashes clearly, there is probably a problem with the device. This can be caused by a faulty ballast.