Don't sell - that's one of the best buy signals you'll see!!!
The NAV went up - that means the underlying assets are worth more - that's what you want to see
The cost to buy that NAV went down - shows dumbness of the crowd - evidently they don't like to see an increase in the real value of their stock (NAV)
My opinion = this is a strong buy signal...if you haven't jumped in yet...jump
if you have, hold what you got cause it's real worth is increasing and the price will return when the dummies get their minds focused on real worth again....then sell.