I'm also interested in this bug. The issue is triggered by the fact that
tell application "Orion" to get the windows
returns many more windows than expected. My Orion Window menu only has one Window, as shown in the attachment:

but the result of the code above is:
{window id 12157 of application "Orion",
window id 11331 of application "Orion",
window id 11541 of application "Orion",
window id 11536 of application "Orion",
window id -1 of application "Orion",
window id -1 of application "Orion",
window id -1 of application "Orion"}
If I try to find out how the other windows are different, with code like this:
tell application "Orion"
repeat with theWindow in the windows
get properties of theWindow
end repeat
end tell
It fails with the same error "Orion got an error: AppleEvent handler failed." number -10000
error message on the second window.
So there is probably some hidden windows or window-like objects being reported by get the windows
that are not true Orion document windows.