I've noticed Xayah's feathers disappearing or sometimes not coming out at all.
Copying info from a post someone else made on the EU live forums:
1: SG Xayah W is bugged. If you use W after an auto attack she does not send out a feather even though she loads up three and you should send one out from attacking. This has lost me several kills and escapes. She will just get empowered, auto attack, and won't send out feathers till the next attack. (Example, Auto Attack Vayne, Press W, Issue another Auto Attack, that second auto will not produce a feather behind Vayne. The following Auto will)
2: If SG xayah or rakan recall and the other joins them. The SG music immediately skips to the end instead of continuing where the original recaller one left off. This is so jarring to hear the music just cut to an end.
3: If you use /Joke next to a SG Rakan as SG Xayah you will hear the VERY END of the Original Xayah and Rakan Joke. Either Xayah says "Why Now" in response to Rakans original saying "Kiss Me Baby" . Or She says "Nice to Unmeet You". You do NOT hear Rakans voice line though. And the SG skins even have their own jokes. So this is inexcusable as to why this doesn't work.
4: SG Xayah when uses R doesnt change to her uncorrupted form like she is supposed to (Been happening since patch 9.20 ) Before that it just didn't last long enough. It should last until death like Eclipse Leona and High Noon Ashe. That fits the lore better anyway since Xayah turned corrupted after dying.
5: SG Rakan cant for some reason use W in same place as where he is standing. (Been happening since patch 9.20 but that bug doesnt happen all the time. its random)
6: Not a bug but a small issue with the voice lines. Xayah still has her "I'm so tired... Everyone is counting on me" voice line when using SG Xayah. This makes absolutely no sense to the skin. None what so ever. No one is counting on her anymore as SG Xayah. It's so out of place and the fact that no one at Riot thought to remove this specific line is ridiculous.
7: The pairings can no longer hear each other. I play with my friend who has Rakan and when I use the joke even thougu it's bugged or if Xayah says one of their joined quotes, she hears nothing. You used to BOTH be able to hear when the other talked to each other. It's the entire pull of their voice lines and the fact that it's broken with these skins is disheartening.