What is the reason for the fragility of euro-zone bank bond and equity markets?

In th e recent period there have been very drastic movements in risk premia on euro-zone bank bonds and i n the share prices of euro-zone banks. What is the reason for this fragility of euro-zone bank bond and equity markets, when default rates are low, the level of non-performing loans is declining, and banks have substantial capital? Plausible explanations are as follows: The correlation between sovereign risk and banking risk means that banks’ situation deteriorates whenever there is pressure on government bonds; The yield curve is flat and is expected to remain flat, and this hurts banks' profit margins; The banks' profitability is low, due to the flat yield curve and rising risk premia on their bond debt, when growth is now slowing.