This appears to be an old bug that has returned or was never completely fixed.
After doing an account reset the first transaction in the ledger (typically the Beginning/Opening balance) get set to a random number. This throws off the account balance which you notice the next time you reconcile.
Is there any acknowledgement of this bug from Quicken (Intuit) and what is the plan to fully fix it?
A workaround is to either 1) put the real beginning balance in the memo field or 2) create a dummy first transaction that gets changed by the bug that you can reset to zero.