Occasionally I get a bug where the nameplate of a mob is showing, but the bar itself is transparent. It throws no errors at all when it happens. I have no clue how to duplicate it besides just running wild until randomly one enemy will have it. Sometimes more. It can get rather frustrating. I've known others to get this issue, and my scouring of the current issues and closed couldn't find any issue mentioning it. Sometimes spamming V to hide and reshow the nameplates will make it reappear, but not always.

Secondly, I get an issue with pets. Where they also similarly get an invisible nameplate but no name like the above. It looks like below.

Edit: I wanted to mention I am also on Release version 2.18.1

Alright, after having run around for a lengthy enough time and not finding a single instance of it, I'll chalk it up to TRP3's module. I'll let the proper people know and maybe see if they can do anything about it

This is almost always due to a third party modification (including the custom scripts I provide). What's the output of /knp dump?

This is the current dump of it (though the bossmod control visibility was recently changed, it seems to appear on both having it on and off):
2.18.1 2.3
{ ["profile"] = "default" }
{ ["bossmod_control_visibility"] = false, ["cvar_show_friendly_npcs"] = true, ["clickthrough_self"] = true, ["cvar_personal_show_combat"] = false, ["cvar_max_distance"] = 100, ["cvar_enable"] = true, ["mouseover_glow"] = true }
HealthBar, CombatUpdate, NameText, [LevelText], RaidIcon, [ClassPowers], CastBar, Highlight, PowerBar, AbsorbBar, Threat, Auras, Classification, Execute, TankMode, Fading, GuildText, [CombatToggle], ArenaID, BossMods, BarAnimation, PlayerAnchor, Target, Total RP 3: KuiNameplates

Try disabling TRP3:KuiNameplates.

Sorry for the late update, as I lost internet pretty much immediately following my last post. Upon disabling the TRP3 module, the pet names have returned, but I'll need a bit longer to test the other issue, seeing as I can't repeat that at will, but I can find a hunter in the city easily.