Investment Data Corruption

Windows local version - I've used Quicken now for over 35 years and this has never happened before. Each day, I update my investment portfolio online. Two days ago, one of my accounts was up unexpectedly by $100,000. On careful review, I discovered it was showing 3 stocks that had been sold years ago. When I viewed the stock details, the sale info was no longer there. I restored the backup from the day before and updated again and all was back to normal. However, this afternoon, the account was up over $250,000 and this time it was in the cash account. I opened the register and it showed the correct amount. I went back to the portfolio view and the number was now correct. It's acting like intermittent and temporary data corruption. Any ideas?