Right after the negative price settling, I received notice from several of my trading platforms that the June contract would be closing only, treated as expiring contract much earlier than normal. This, I guessed, would lead to a buy only to cover shorts and no shorts jumping in, thus continuous rise of the price. I quickly cancelled my option spread offer for much lower price for the contract. I was right in my intuition, the price shoot up continuously since with little looking back.
The negative price with these platforms not being able to quote the correct price is the first blow, the change of trading limitations by these large platforms is the second blow. CL is forever deleted from my swing trade list, I will only trade scalping intraday, if at all. But I am a retail small trader of CL, not the trend maker. But I have made my choice.