When you are looking at a record, ask yourself: was this record created all in one sitting? Or was this amended and updated over time?
There are different types of records that were changed and updated over a longer period of time. In population registers, people who moved out or died were crossed out, and people who moved in or were born were added. In some types of tax or tithe records, owners of real estate would be updated if the property changed hands. In cadastral ledgers, plots that are sold or transferred to someone else are crossed out, and plots that were acquired were added. It helps to think of these types of records as videos, since they capture a longer period. Not all the data in the records was valid at the same time.
Even records we usually think of as snapshots may include updates. An example are the notes in the margin of a child born out of wedlock, that was later acknowledged and legitimized when the mother married.