Judging by the 'quality' of construction it could be one of units from a well known 'low buck' Taig system dealer (before they went with the G540 driver.) However everybody and his brother makes stepper drives these days with the same chipset as you have on your driver board (they are inexpensive). Many of these are not very well done (I have seen a few that were well designed.) Given a poorly designed board the stepper driver chips will fail on a regular basis.
You can also damage them quite easily by turning the stepper motors by hand, which lets the motor act like a generator sending power into the driver.
You can probably find a similar drive board to swap in or spend a bit more and get a higher quality unit that won't give you any more troubles.