Firstly, I don’t think that minor frosting, just in the morning is significant, as long as the air movement has an opportunity to continually dry it out.
I posted in your other thread, that I believed you needed to beef up your Total NFVA and the only recognized way of doing that, as per the most accepted ventilation theories is to increase the amount of intake ventilation.
A) Firstly, did not have the vapor barrier, which you have since corrected.
B) Does not have a “Balanced” ventilation scenario.
Due to item B) you were required to have ventilation installed at the 1/150 rule, rather than the 1/300 calculation.
At this point, I would just keep an eye on the frost and see if it looks like it is permeating the deck sheathing.
Also, Coravent is one of the inferior ridge ventilation products. (Yes, that is just my Opinion, but most people and contractors value that highly, especially regarding ventilation) It does not contain the External Baffle, like the Shingle Vent II or the Cobra Snow Country Ridge Vent products, so the roof material price saved a few bucks on the material cost, but does not provide the most optimum performance. You should have been aware of that fact when you did your initial research.
Since you wound up with the weaker and cheaper version of plywood, it Will be more susceptible to future bowing and buckling, as you already have experienced. This will more than likely continue on for the life of the roof, unless you add a continuous soffit strip vent along the entire perimeter of the upstairs 2nd story portion of your home.
Also, due to the pitch of your roof, which if I recall, was about an 8/12, there is increased cubic footage of contained air space, which should be vented at an additional 20% to 30% capacity, regardless of the 1/300 or 1/150 formulas, to compensate for the additional air contained within the attic environment.
One final point about the option of utilizing a PAV, Powered Attic Ventilator…I do not think that you have sufficient enough intake ventilation to properly allow the fan to expel the air as required. I will try to look that up for you.
If you don’t mind, I would like to relay your thread on a Building Science Forum that I participate in and relay advice regarding proper ventilation techniques to other contractors and home builders.