In the recent redesign of the `website_event` module(s) [1] a field was used in the templates of event_track that only exists if event_track_live is installed. The `t-att-class` argument is now overriden in `event_track_live`. task-3597612 1: 94c5bc3d152c80fdbb6798d9b4d28bf62740856b closes odoo/odoo#142215 Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>