Hi Kassa,
It may be that someone has seen something similar to your situation, but perhaps some more specifics would help.
1. What hardware/instruments are you trying to interface with?
2. How are you interfacing with this hardware? DAQmx call in a code module? What kind of code module are you using? LabVIEW, C, or some other ADE?
3. What is TestStand doing when the instrument "goes missing"?
4. What version of TestStand, drivers, software are you using?
Once we get some more specifics about your issue, it will be much easier to narrow it down to the source and give helpful feedback.
Jorr-ElSystems Engineer