Custom Filtering

I have a data set for incidents that gets a little messy. There should be two or three records for each incident ID (created, acknowledged, closed) but not all incidents are acknowledged (well most incidents are not acknowledged, but that's a whole different discussion). To make it juicier, sometimes the very thing causing the incident disrupts the ingestion of the incident data itself so sometimes I only get the open, ack, or close by itself. (An example of the raw data pulled into Power Query after removing unneccessary columns can be found in a comment below.)

My first problem is to calculate the duration in minutes between the first and last incident with the same ID. I have something that seems to be working there, but is probably inelegant:

The bigger problem is I need to display these as a single line, which means removing all of the rows that do not have calculated durations except those that only have one record. For instance:

So I need to:

DISPLAY all rows WHERE (
	"Prev.INCIDENT_ID" IS NOT NULL
)

DISPLAY all rows WHERE (
	"Duration" IS NOT NULL
	OR (
		"Duration" IS NULL
		AND
		"Incident ID" NOT EQUAL to "Prev.INCIDENT_ID"
	)
)

So, I tried:

let
    Source = ||SOURCE||,
    #"Removed Columns" = Table.RemoveColumns(Source,{"ALERTS_ID", "ACCOUNT_ID", "ACCOUNT_NAME", "CONDITION_ID", "CONDITION_NAME", "INCIDENT_API_URL", "INCIDENT_URL", "POLICY_URL", "CHART_URL", "EVENT_TYPE", "ID", "NAME", "LINK", "TYPE", "SERVICE", "PRODUCT", "TEAM", "UPLOAD_DT_TM", "UPDT_DT_TM", "PARAMETER"}),
    #"Sorted Rows1" = Table.Sort(#"Removed Columns",{{"INCIDENT_ID", Order.Ascending}, {"TIMESTAMP", Order.Ascending}}),
    #"Added Index1" = Table.AddIndexColumn(#"Sorted Rows1", "Index1", 0, 1, Int64.Type),
    #"Added Index2" = Table.AddIndexColumn(#"Added Index1", "Index2", 1, 1, Int64.Type),
    #"Merged Queries" = Table.NestedJoin(#"Added Index2", {"Index1"}, #"Added Index2", {"Index2"}, "Prev", JoinKind.LeftOuter),
    #"Expanded Prev" = Table.ExpandTableColumn(#"Merged Queries", "Prev", {"INCIDENT_ID", "CURRENT_STATE", "TIMESTAMP"}, {"Prev.INCIDENT_ID", "Prev.CURRENT_STATE", "Start Time"}),
    #"Added Custom" = Table.AddColumn(#"Expanded Prev", "Difference", each if [INCIDENT_ID] = [Prev.INCIDENT_ID] and [#"Prev.CURRENT_STATE"] = "CRITICAL" and [#"CURRENT_STATE"] = "OK" then [TIMESTAMP] - [Start Time] else null, type nullable duration),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "Duration", each [Difference] * 1440),
    #"Reordered Columns" = Table.ReorderColumns(#"Added Custom1",{"INCIDENT_ID", "TIMESTAMP", "Start Time", "Duration", "POLICY_NAME", "DETAILS", "SEVERITY", "CLIENT", "CURRENT_STATE", "OWNER", "TENANT_ID", "Index1", "Prev.INCIDENT_ID", "Prev.CURRENT_STATE", "Index2", "Difference"}),
    #"Removed Columns1" = Table.RemoveColumns(#"Reordered Columns",{"TIMESTAMP"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Columns1",{{"INCIDENT_ID", "Incident ID"}, {"POLICY_NAME", "Policy"}, {"DETAILS", "Violation"}}),
    #"Custom Filter1" = Table.SelectRows(#"Renamed Columns", each [Prev.INCIDENT_ID] <> null),
    #"Custom Filter2" = Table.SelectRows(#"Custom Filter1", each ([Duration] <> null or ([Duration] = null and [Incident ID] <> [Prev.INCIDENT_ID] and [Prev.CURRENT_STATE] = "CRITICAL")))
in
    #"Custom Filter2"

This has given me the closest result to what I need, except it occassionally returns the Open incident and the Closed incident records following a single Open record entry.