Aye the air venting is main thing that may cause your problem...
In my previous tent wasnt that many venting i do get the same problem as you...until i bought the new tent that come with good air venting all around the tent, never had that problem again.
so try keep your venting open all through night and wrap urself warm, in good quality sleep bag or stuff that make you warm while venting is open...
I left my all venting open in 2 weeks camp and never had any problem..lucky its was hot all 2 weeks..
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