I have the exact same problem described in this post
For instance, I have a checking account for which I have transaction history starting 1/1/2021. I've had the account for longer, so I have an Opening Balance transaction entered on 12/31/2020. That transaction has disappeared many times. The pattern goes like this
- start balancing accounts
- notice that the balance of that account is off
- look back through previous statements to find when the discrepancy occurred
- discover that the opening balance transaction has disappeared, again
- enter it and reconcile it
- sync my Quicken data to the cloud
Within a couple of months, it happens again. That is the most consistent transaction that disappears. Transactions do disappear from other accounts.
- It's usually just 1-2 transactions
- Usually from a previous year
It happens with the aforementioned account into which I import transactions manually and in accounts for which Quicken automatically downloads transactions.