In betalabs, reset your preferences to see guided tours on RC and Watchlist. The guided tours will not display rc-beta-tour-welcome-ltr.gif
https://en.wikipedia.beta.wmflabs.org/w/extensions/WikimediaMessages/modules/images/rc-beta-tour-welcome-ltr.gif gives "Unknown file path".
Thanks to @Volker_E's debugging, it seems that it happened due to changes made https://phabricator.wikimedia.org/T196033.
Note: Giuded tours are fine in production.