I have added most of my comments in the screenshots below describing the error I'm receiving and how my program is setup to run.
The error occurring only when adding in the "Write to DO.vi" doesn't make sense to me. Without it, the timed loop executes well under 1000 microseconds (200-300us on average). I don't think that something else is in my program that is causing this error and the high loop execution times because without that VI the times are fine and there are no errors.
Is there something I am missing in the setup for the DO card that is causing the "Write to DO.vi" to take up a lot of time in the timed while loop?
The only other thing I can think that may be causing this issue is that the DO sample clock may not be able to keep up with the sample clocks of the other cards. Here is the DO card we're using and there isn't any specifications for the clock rate and I couldn't find any in the datasheets or help manuals
I have saved the LabVIEW project in 2019 and attached it. I've been stuck on this error for a while so I'd appreciate any ideas and I'm open to any suggestions for what to try.