Each parameter has to be getting what you expect. In this case, the event parameter was getting passed self (in this case the ResourceTrackFrame table) and the event landed in arg1.
Add "PLAYER_ENTERING_WORLD" to the registered events and
Code:
local function ResourceTrackFrame_OnEvent(self, event, arg1)
print(self, event, arg1)
reload the ui.
What you name the paramters doesn't matter, it is what they are passed that counts.
Code:
local function ResourceTrackFrame_OnEvent(amanda, marge, sue)
print(amanda, marge, sue)
reload the ui.