Hello elliotreid!
To see what trials in which it happens, create a version of your .csv input file that has no randomization (i.e., it uses only values of 0 in the bgr and wgr cells). Then, run a session and keep track yourself about which trials malfunction. You can also refer the file named TrackPerformance.txt in the DirectRT program folder to see if there were any errors logged during the DirectRT session.
Please also feel free to send me your DirectRT files and screenshots and I will be happy to look at them. You can either upload them here or send them to support@empirisoft.com (please refer to case 22026 in the email).
Jason Reed
Empirisoft Software Support Specialist