Siemens Simovert VC dual faults?

Gentlemen,

I have two rollers in a system that operate in tandem. They are both driven by Simovert VC Masterdrives, and I am not sure about their master/slave status at this time, but they are connected to each other via fiber optic cabling. Twice in the last couple of weeks I have received these faults: F008 "DC link undervoltage" on one drive, and F026 "UCE shutdown in phase 2" on the other drive. My main question is: which is causing which? My second question would be: what is UCE?? You guys have really bailed me out of a serious issue in the past and I look forward to the day that I have enough knowledge to return the favor, or at least to pay it forward. In the meantime, I need help!!

Manual here: http://www.mawos.com.pl/Files/MASD_OI_EN.pdf

I never got to the bottom of what UCE stood for, but all the F026 I have had have never been an short circuit, but either a fault in the monitoring circuit in the drive or excess cable capacitance due to a long run of cable.

I was reading about UCE last night after I posted this and the most common thing I was reading to check the IGBTs in the drive. I will not have a chance to do this until it goes down again or during our scheduled shutdown next week. I cannot imagine it would be an issue with the cabling, as this system has been in operation for almost 15 years. Unless, of course, something is breaking down after all that time. Does it still make sense that it could be in the monitoring system of the drive if it will run for a week (approximately) before it trips on this fault?

how did you solve fault F008 (DC link undervoltage)? thanks