Are "order by time desc limit 1" and "last(field)" different in behaviour?

I am using 2 queries
Query 1: Select "field1",field2,tag1 from measurement group by tag2 order by time desc limit 1 and
Query 2: select last(field1),field2,tag1 from measurement group by tag2

Both these queries are giving 8 ouput lines. I expect the output of both the influx lines to be same but there are incosistencies in at least 3 output lines. The timestamp for those mismatching lines is same and the only inconsistency is in value under tag1 tag.
can some help me understand how both queries are different as they are giving different outputs?