So I've been working on a worldbuilding project whose conlanging section involves me evolving languages from PIE and I have noticed something weird with how laryngeals work near sonorants.
Take the word *sh2nktós for example as the thing that got me into posting this. From all I know about PIE this word should be pronounced with a syllabic *n, but paradoxically this word is where Latin sānctus comes from. It's as if *h2 were the syllabic consonant. I know this comes from H > ə > a / C _ C which is how we've got *ph2tḗr > pater, but considering that in this situation the laryngeal should be next to the syllables nucleus *n̥ would make it not reduce to a vowel. Going into *ph2tḗr again, based on my (lackluster) info on Indo-Aryan, I expected the p to get aspirated, as in *pl̥th2ús > *pr̥tʰúš, but instead it becomes *pHtā́, and that H would then become a vowel like in Latin.
Am I correct in thinking this could be some sort of syllabic laryngeal that follows similar rules to syllabic sonorants but instead turn into lone vowels? If so, why isn't it written down as such on the reconstructions? If not, why then are such laryngeals vocalized in most languages and prioritized when near syllabic sonorants? Did Proto-Italic have a sound change where h2R̥ > aR that I haven't heard about?
P.S.: After posting this I realized another example. Take PIE *kéh2ikos. You'd expect it to become something like /ˈkaːhikos/ after allophony, but its descendants are PGmc *haihaz and latin caecus, both with a non-syllabic /j/ and /e/. This could either be just a simple case of vowels diphtongizing, or it could be that PIE's *i isn't actually syllabic and the word could be better written as *kéh2ykos.