I'm having the exact same problem on my Verizon LG G4.
No changes in apps/usage for the past two months, and all of a sudden a few days ago I have been experiencing high battery drain.
It seems to be correlated to having WiFi on, but is independent of the access point (happens at home, work, friends house). Shutting off WiFi in good service areas seems to fix the problem, but my 4G service seems to have gotten worse lately the phone often switches to 3G or 1x indoors. I am running the latest Verizon software (27C).
I have tried rebooting the phone several times with no effect. Top apps on the battery usage screen are always Kernel/Android OS (~25%), Android System (~20%), and Google Services (~5-10%). Everything else is <2%. I have cleared app cache for the top 10 apps.
Any ideas?