I use an AS5300 with 240 mica modems and sometimes when I need to turn off the power after I turn it on again not all the modems seems to start correctly. Most of them fail in the C state when I am dialing out. And surprisedly they start to work again after some days with the power on.
I tried to reset them, reload the firmware, and another maintenance commands.
But nothing seems to work just time to them "warm".