I had a Nexus 5X die within the warranty period, and had a similar experience. LG's support was utterly awful, it took them 3 weeks to replace the phone.
They originally told me I could get a replacement 5X, then they told me I could get a T-Mobile G5 and what they eventually sent me was an AT&T specific G5 that required digging into config menus before it would connect to T-mobile LTE.
Big company support have lots of moving parts. My girlfriend's Nexus 5x also died this week. Local LG branch (Budapest) replaced the motherboard within a day. She basically got a new phone for free.
They originally told me I could get a replacement 5X, then they told me I could get a T-Mobile G5 and what they eventually sent me was an AT&T specific G5 that required digging into config menus before it would connect to T-mobile LTE.