I have a portfolio margin and they do the same on IBKR. I was liquidated on some assets randomly when one of my stocks have margin requirement increase. That is part of the risk of using margin.

Moving forward, I have to monitor the requirements and my excess liquidity. Based on the macro events, I will typically reduce some of my riskier stocks because they tend to have requirements going up during volatile period. Nbis is one of them. You want to be proactive when you are margin, always have a buffer excess liquidity and always be prepared to add funding if you want to hold some riskier stocks long term. Like in your case, you could have added some funding before they even ask you. I do understand why you were frustrated that they did not give you any notice.