The end of June has always been a moment of truth for the financial system; several categories of debt are due in various places. This year, for the European Central Bank, there are almost a half-trillion euros due, from the loans made under the Targeted Longer-Term Refinancing Operations—the TLTRO loans. Not all banks have the money.
The TLTRO are a low-interest loans facility implemented by Draghi in 2004. The ECB is not going to roll them over. It is estimated that €476.8 billion of debt is due on June 28.
According to Bloomberg, Italian banks have more debt than liquidity parked at the ECB, so that they must find €35 billion this year and €85 billion next year to be able to pay the debt.