"Do you notice that this occurs during any specific times (when an output or drive turns on or off)?" I don't know because i'm told about it a few hours after when it happened. This unit is instaled in water treatment station, So when water reaches low level limit then others device like pumps was stopped and personel knew about problem with PLC, but like i said problem started a few hours before. During this few hours Plc notice alarms (like low limit level of water) but don't execute rest of program like start subpomps to produce water. "When you checked the voltage and current was this when the unit was displaying the black screen? When displaying the black screen is the I/O units still receiving power?" No, i checked it when PLC run properly, i must wait when it will be happen. I was changed SI9 to 20 in "screen saver" maybe error code will be displayed on the screen .
"The voltage is slightly high since the V1210 runs on either 12 or 24VDC. " In Technical Specifications of V1210 is writed that permissible range of voltage is 10.2-28.8VDC. By the way this type of power source is often used in similar systems and i don't have any problems. I measured Voltage on power source and on Vision, current only on output of power source. "Also, does this occur with any other similar system or is this isolated to this individual unit?"
One time i have problem with similar system but i finded a problem. It was broken earth screen of level probe that was causing a short circuit between grounded earth and 0VDC.
After replacing level probe the problem disappeared. In this system i checked it. There was the same problem with radio modem Satel (there was factory-made ground to 0VDC of modem). I isolated the power of modem from Vision and i changed communication, between Vision and modem, from RS 232 to RS 485.