i've not experienced regular enough hospitality encounters to be able to notice trends. but i will also call it grating

Can't say I've heard this one, but the one grammatically incorrect phrase I hear all the time is people asking questions like "How to ___?" instead of "How do you ___?" I can only assume it started with people typing "How to ___" into search engines, since the titles of whatever article they're looking for would start that way, but somewhere along the way people started phrasing their questions on forums or occasionally IRL that way. It's not a huge deal, but it makes my eyebrow twitch whenever I see it.