Strange issue - data and email results the same but email doesn't come on execute, only on preview

To keep things simple, Email snap is set with Validate & Execute so that it will fire on preview tests as well as execute.
Data is simple, pulls 46 rows from a table, merges the count i.e. 46 and sends the results to an email. Email comes reliability with preview every time. But when execute, it goes all the way thru, same results, same data but no email.

One other REALLY weird thing I found is when pulling a date/timestamp field to build the query and get the 46 rows, if the field is set to pull using Date.parse($LAST_RUN_DATE.Timestamp).toString().substr(0,10), the date returns to “2019-01-01” and results continue fine, preview sends email, but execute does not.

If I adjust this expression to be hard coded i.e. Date.parse(“2019-01-01”).toString().substr(0,10), which also returns “2019-01-01” and results continue fine but preview AND execute send email. What in the world?

Please advise.
Melissa