Trip clearly erroneous dates
If a project ends at a certain date (say 1930) make it so that a person can't enter a date later than that. I've repeatedly seen records that have the French Republican Calendar deliberately misindexed by someone too lazy/malicious to calculate it and rather than leave the field blank and return it, they make up a random date wildly out of synch with the rest of the batch. This should not be possible IMO. The project in question (Saône et Loire Registres Civiles) goes from 1511-1930. I've seen 42 BCE and 2009 among other dates. Unacceptably frustrating, especially because then it can be very tricky to attach the person to a record. Am I SURE this person is dead? It says they got married in 2009! Yes I'm sure. He was born in 1750.