This has happened to me on several occasions over the past few years and I cannot readily reproduce the error. Take a look at the register (basic bank account) in the attached screenshot. $58,569.12 - $6000.00 does not equal $56,185.50. If I exit Quicken and restart it, the error goes away.
Running a file validation returns no errors.
Version R30.14 Build 27.1.30.14