Not sure whether this is a bug or a "feature"...
For fields having a coded value domain or a numeric range domain, the continuous collection style in Collector does not necessarily repeat the value from the previous record, but it does repeat the value from the last time the field had a non-NULL value during that session.
For instance, say a value from a coded value domain was selected for a field in the first record. In the second record, the field’s value was manually changed to NULL because the field's value wasn’t relevant for that particular record. When continuous collection style is in effect, the third record will populate that field with the value from the first record…the last time that field actually had a value, not the value from the previous record where the field had a NULL value.
My expectation was that it would faithfully bring forward all of the previous record’s values, whether they were NULL or not.
Continuous collection works as expected for fields that do not have coded value or range domains.