Compare Previous Two Rows with a Current Row using DAX

There are newer DAX functions that are similar to SQL's LAG. For example, OFFSET:

IsSiteDown =
VAR Summary =
    SUMMARIZE (
        Table2,
        Table2[sitename],
        Table2[category],
        Table2[firstoccurrence]
    )
VAR Prev1Cat =
    MAXX (
        OFFSET (
            -1,
            Summary,
            ORDERBY ( Table2[firstoccurrence] ),
            PARTITIONBY ( Table2[sitename] )
        ),
        Table2[category]
    )
VAR Prev2Cat =
    MAXX (
        OFFSET (
            -2,
            Summary,
            ORDERBY ( Table2[firstoccurrence] ),
            PARTITIONBY ( Table2[sitename] )
        ),
        Table2[category]
    )
VAR Result =
    IF (
        Table2[category] = "Site Down"
            && Prev1Cat = "Low Voltage"
            && Prev2Cat = "AC Mains Failure",
        "Yes",
        "No"
    )
RETURN
    Result