Menstrual cup leaking

alice

I've been using the lena cup and overall its been great but it seems very hit or miss with leaking. I'll insert the cup and check to see if it's open and tug the stem a bit to see if there's a good suction and everything seems good until I go to the bathroom and see its leaking. I'll take it out and it's not full and reinsert it the same way and it wont leak. What am I doing wrong?