Were you doing something at the time? As in, did taking a specific action within the game trigger the error message?
I tried to use cloth calc script to import my character, and it failed, and said to check to see if the "completed" quests tab worked. When I went to check, it gave me that screenshot error message.
The first thing I did was remove cloth calc from my Chrome extensions, cleared all cache and closed all windows, then logged back into the game, and went directly to the completed quests tab, and it showed the same error once again, so I don't think its related to cloth calc.
I also logged into The West using Microsoft Edge on a different computer, which I considered would be "fresh" as I don't use Edge for anything, and again, same error.
In between the last time it worked and the time it failed, the only thing I did was two (2) hour long "White water transport" jobs, and slept for a few hours in a foreign city hotel.