Claim viable: EKHG strict liability applies, carriage contract strengthens the position.
Where an adult passenger falls as a result of an operating error (excessive chair speed, absent assistance, failure to stop), the EKHG strict liability applies directly. You need only establish the damage and its causal link with the operation of the installation. The operator must prove an unavoidable event under Section 9 EKHG, which under OGH case law regularly fails for staff or operating errors.
In parallel, the carriage contract strengthens your position: the reversal of the burden of proof under Section 1298 ABGB means that the operator must prove compliance with all duties of care. Secure evidence now: keep the lift ticket, request the slope-rescue protocol, note witnesses, take photos of the boarding or alighting zone.