Hello Mr. Dowson,
Thank you for the time and effort that you are putting into FSUIPC 5. I wanted to provide some feedback that may be of use to you. I have a registered version of FSUIPC 5. I am currently using beta version 5.101j.
Under the Button + Switches tab, I am attempting to allocate the "kneeboard view" to a button on a CH Yoke Eclipse. After saving this button allocation and resuming the sim scenario, my scenario is fine until I access the Kneeboard with that button. Upon using that button, the Kneeboard will display, but then all of my FSUIPC defined buttons and axes immediately become inoperable. However, the sim does not freeze. If I go back into FSUIPC and clear "kneeboard view" from the yoke button, everything is fine again. This issue occurs whether or not I am using default aircraft or add-on aircraft.
I've attached the LOG file below. Let me know if there's anything else that you would like me to provide.
FSUIPC5.log