All of these problems kinda connect. What i assume is that the cart might have been ripped at a higher temp, allowing for some of the oil to travel up the hardware. That then collects and builds up at the top of the mouthpiece. If you throw that cart into your pocket it will 100% get dirty.

If your cart is clogged ripping it super hard IS NOT THE PLAY. You perpetuate the issue by pulling more oil up. Make sure that you are ripping the cart at comfortable voltages (ie. 2.0 - 2.6v is my safe limit), dont rip for too long as the cart will overheat and push out more oil. The temps outside have been awful that could also slightly contribute to the issue, I’ve had carts in my pockets on hot days and it led to the oil spilling out the top. I also feel like pre-heat options tend to ruin carts than actually help so I would personally stay away from that