Since the error msg states something about the origin,
I'm assuming that the error is related to the following line of code:
.setOrigin(google.script.host.origin)
I'm guessing that the google picker is designed to test for whether
the picker window, and the window that launched the picker have the same origin.
I believe that this is to avoid cross browser security issues between open tabs, like
code injection attacks coming from a different browser tab to execute malicious code.
From the error msg we don't know whether the issue is from the browser, the Google picker, a Google document or Apps Script, or a service error.
You could test your app from different browsers to determine whether it's a browser specific problem.
If the Google picker code, and Apps Script code related to the picker haven't changed, then I'd guess
that it's more likely to be a browser issue?
I don't know of any other alternative for
.setOrigin(google.script.host.origin)
google.script.host.origin is a Google client side API.
I don't know if this could be a temporary service error.
It's hard to know what the origin of the error is.
I'd try the picker in different browsers first.