Watch Dog Timer
He will reset the board for you if it freezes.
That looks like a decent link but I didn't watch all of it.
Alternatively, you can have the watchdog fire an interrupt instead of resetting the board. In said interrupt, you could stop the servos.
Although the much much better path would be to figure out what is locking up your program and fix that.
There is no fix - the watchdog oscillator is a very minimal implementation.
Why does it matter?
Anyone knows how to fix this?
You've been at this long enough to know what I'm about to say.
Not without seeing the ....