Usually the source of such problem may be:
- the bulb itself
- the lamp housing
- the cable (rarely)
- the power supply.
Which exactly model of Acuity you use?
First of all - swap bulbs between lamps (wait first until they are cold, don't burn your fingers!) and check, if the problem stays in the right lamp (that means that the bulb is not a problem and you need to look somewhere else) or it moved to the left lamp (now you know, that it's the bulb). If it's not a bulb, put them again in the positions they were at the beginning (so swap back) and check, if all fans on top of the right UV lamp are working (if not, hot air circulation may be too low to give proper cooling). If all fans are working, try to swap cables connecting UV lamps with the power supplies (it may require to undo some screws in the carriage, don't forget also that you may unplug the cable only when lamps are cooled down, otherwise you may damage the reflector inside the lamp) and check again if the problem moved. It's also possible that one of the power supplies or cables is damaged, but the diagnostics requires the SDS key or at least logs and someone who can read them. Check also, if the ventilation holes on the UV power supply box are clean, sometimes the power supply itself may overheat (try to print anything without cover, but be VERY careful - there is a high voltage inside!!!).
Unfortunately you can't swap housings, as they are different. But you may also swap the power supplies (cables on the PS side).
Everytime you want to disconnect anything, wait until lamps are fully cooled (fans on the top are off), otherwise you may damage the lamp itself (not the bulb). And don't forget, that you can't touch the bulbs with bare hands, use cotton gloves (I use nitrile gloves and cotton gloves on the top to be 100% sure that I don't leave anything on the bulbs).