Motu Ultralite s/pdif white noise problem

Anyone owned one of these units and had problems with noise
 

• Basically turn the unit on (Motu Ultralite mk3)
• All is ok and runs well
• after about 10 mins use it develops white noise through the monitors (visually displayed on the screen and the s/pdif input in cue mix software). I can mute the sound but it is always there
• If alter a sample rate or clock setting the sound goes as I apply it but then comes back within seconds
• Finally I have just the power supply connected and only the monitors (no firewire,no usb, no hardware), and it replcates the same problem indicating it is not computer or software based but with the Ultralite itself.

Has anybody heard of a fix for this

Thanks.
 
Also does it when not connected to computer and in stad alone mode also.
 
It seems apparent now as from Motu technical support that it is a calibration issue on the spdif port chip within the unit.
 
Theres a procedure for connecting it to another unit(via spdif's) then opening up the case and turning adjuster screw until the noise stops.
 
Not ideal, but will do it when I get some time and hope it cures it (Motu says it will).