This has happened to me now as well!

I closed out 2023 with everything tying to the penny. When I went to reconcile my current month, it's stating that there is a $33k discrepancy. I ran the suggested report, as with 90% of their available reporting, it's useless. It's essentially an audit log in a different format. There are dozens of reconciled transactions that do not match up in any way to the discrepancy amount.

I went out to my bank statements and verified against the prior reconciliation reports in QBO as well as the past copies I downloaded at the completion of each reconciliation. The beginning balance, credit, debits, and ending balance on the reports and bank statements match to the dollar. I confirmed it in the chart of accounts all the way back to the opening of the account in 3Q2023. I went out to the chart of accounts and when line by line from Jan - May 2024 against the bank statements. There are no additional transactions, missing transactions, or unreconciled transactions. There are no other items in the chart of accounts reflected that would cause the reconciliation portion to do this. It's stating that the beginning balance is what's off. That's literally impossible. 

QBO just did a massive update that created new "features". My guess, they didn't code something properly, which is what's causing the issue. I moved from desktop several years ago and we've had nothing but issues with QBO. From things changing constantly, to mapping being incorrect or changing, to their platform being inaccurate. I'm not even sure where to begin to handle this. At this point, to ensure I have the bank reconciled to the chart of accounts and my other reporting correct, I'm by-passing the reconciliation process all together. I'm doing it manually, line by line from the bank statements, and manually reconciling to the chart of accounts. My guess QBO will realize their error and decide they'll fix the issues they caused and it will just miraculously decide to work that day. Be prepared though, you'll have no idea when they fix it. You'll just go in several days, weeks, or months later, and poof, fixed like it never happened.