Since the Osram Duka 10 safelight fixtures use European 4 foot 40W T12 preheat fluorescent tube ballasts to drive Na10FL low pressure sodium lamps, which have a significantly lower arc voltage drop compared to 4 foot 40W T12 fluorescent tubes where the 4 foot 40W T12 fluorescent tubes have an arc voltage drop of about 100V and an operating current of about 430mA while Osram’s Na10FL low pressure sodium lamps have an arc voltage drop as low as 16V and an operating current of about 570mA, I have been wondering if Osram Duka 10 safelight fixtures are very prone to ballast failures caused by the ballast overheating because of the fact that the Na10FL low pressure sodium lamps have such a very low arc voltage drop and cause 4 foot 40W T12 preheat fluorescent tube ballasts to run at around 32% above their rated current.

I don't know of any that failed - i only know it runs pretty hot.

The ballast is likely designed to survive a stuck starter, that continuously lights the filaments in a fluorescent tube. Although it heats up a bit more, and theoretically the life time of the ballast will inevitably be shorter, it might be fully acceptable because safelights often run for a couple hours every weekend, rather than for the entire evening every day.