There is a site that was referenced in a post someone made on FaceBook. One of the pages, listed below, helps with sounds. I haven't had the opportunity to explore it as much as I'd like, but it does show a closeup of the the speaker's mouth. My apologies to the MODs here. I love this course and consider this other site a good support to learning here rather than there. Hope this helps. https://learngaelic.scot/sounds/index.jsp
since medial unvoiced plosives, like P, T, and C, often are preaspirated in Scottish Gaelic, I wonder if this speaker is pronouncing that after the L and causing it to devoice. Icelandic does this sometimes, but I don't think Gaelic normally does (at least judging from what I've read and the other speakers on Duolingo) when there is a consonant before the plosive, so this could be a dialectal feature of the speaker.
edit: unvoiced L's often sound like fricatives, if not becoming one outright, which given the place of articulation, may have it sounding like an S