When browsing responses I get an error in any case: sorting columns, filtering columns, trying to navigate between pages, selecting columns... But it happens on an specific questionaire (as far as I can see) and the behavior changed just recently. I did not do anything different except for changing a token of a participant that already have completed her questionaire. But not sure if things are related, since I found it later. Browsing participants don't show any error. Caches cleaned.