Only way to lift the front tire is from counter-steering or if your kart is bent. If your diagnosis is that there is snap-oversteer (understeer on entry turning to oversteer at apex) then this could be accurate. Front end plows, more steering input to compensate, once you’ve slowed down enough, all that steering input bites you and the rear kicks out.
The solution to snap-oversteer is to gain a bit more front grip on entry so you don’t have to put so much input in.
What’s your rear track width?