DX8100 systems that were made from March 2009 to September 2009 have a problem where the Video Capture cards are constantly sending out errant coaxitron control data, which negatively effects other control systems such as Coaxitron Matrix's. If you can verify the capture card date code (on a sticker on the back of the capture card inside the DX8100), you should be able to get some advanced replacement cards (you buy them, you get your money back when Pelco gets the old defective cards back).
Call Pelco Technical Support at 1-800-289-9100 and ask for DX8100 support, tell them it is in reference to Tech Alert TA090918DX.