Nelo 550 leaking / vent hole?

Hi guys, I recently bought a Nelo 550  (demo) and when I got the ski home I noticed there was water in the hull. I drained it and assumed it was b/c of people flipping the ski with the two-way vent hole. I was told the ski was barely used and only had minor scratches. 
After my next DW, approximately two liters leaked in. I assumed I had a bigger issue and found a hole in the rudder compartment. There was a small area where there was no epoxy on the carbon around the steering tube. Definitely a quality control issue from the factory. I filled this with epoxy and believed I fixed the problem, however when I paddled yesterday I found water in the boat again. There was less water, maybe a cup? If I put tape over the vent for a few minutes pressure will build in the hull and air can be heard escaping when the tape is removed. 

My question to Nelo owners. Do you get water in your ski through the vent hole and how much? I know the amount will vary with conditions etc. Just curious if this is a common thing? 

Mine does admit water if I flip the boat upside down. I am wondering if I should plug it when I practice remounts.  I don't have a larger issue with leaks, but I also don't do much downwind.

My 560 was getting a small amount of water in it when I got it.  The drain on at the top of the desk is a horrible location to put it, all my water was coming in when practicing re-mounting. I installed a straw vent like most the OCs have which has pretty much fixed the problem completely.  The straw sticks up about 2-3" out of the vent, which is enough to ensure it stays underwater when upside down and doesn't allow water in.  Nelo should either do this or change the location/style of the vent.  When surfskis don't use the Gore-Tex vents like SUPs, I have no idea, those work great.

With my 550 I got a little water in through the vent hole when the ski was upside down.
I pushed into the hole a flexible piece of fuel tube from a model shop and sealed the end with a bung. I needed to be careful as the temperature change mean that after 15 minutes paddling i needed to vent the tube accompanied by hissing air in or out depending on an increase or decrease of internal pressure build up.
I have since then stuck a circular piece of self adhesive dacron (self adhesive sail number material from a chandlers) over the vent tube and pierced this with a needle.
The needle hole is enough to allow pressure changes to prevent damage and is too small to allow water in as far as I can tell even after multiple inversions 

Best way to check if the rudder compartment is leaking is to remove rudder, tape the bottom hole, then fill the compartment with soapy water and then blow lightly into the drain hole. This will tell you if there is a leak at the back. there are a few places it can leak, around the rudder post , from the rudder cable tubes and also from the actual housing where there is a thin spot in the laminate ie a hole in the fiberglass.
Around the rudder post is easy and the housing itself but the tubes not so much. If the tubes have come adrift it will need professional assistance to rectify.