Error when saving dataflow: "One or more entities reference a dynamic data source"

I was finally able to figure it out on my own after several more hours of experimentation. Part of it was needing to affix a "?" before the "page=" text. I also simplified the code substantially.

let
  Source = let 
    BaseUrl = pMetricsUri,
    EntitiesPerPage = 100,
    Options = [Headers=[#"Authorization" = "Basic " & pToken ]],

    GetTotalCount = () =>
        let
            Json = Json.Document(Web.Contents(BaseUrl, Options)),
            Entities = Json[count]
        in
            Entities,

    EntityCount = GetTotalCount(),
    PageCount = Number.RoundUp(EntityCount / EntitiesPerPage),
    PageIndex = { 1 .. PageCount},

    GetJson = (PageIndex) =>
        let
            Url = BaseUrl,
            Json = Json.Document(Web.Contents(Url, 
              [
                  RelativePath = "?page=" & Text.From(PageIndex),
                  Headers=[
                    #"Content-Type"="application/json", 
                    #"Authorization"="Basic " & pToken
                  ]  
              ])),
            Value = Json[ticket_metrics]
        in
            Value,

    Urls = List.Transform(PageIndex, each GetJson(_)),
    DataList = List.Union(Urls),
    TableFromList = Table.FromList(DataList, Splitter.SplitByNothing(), null, null, ExtraValues.Error)
in
    TableFromList,
  #"Expanded Column1" = Table.ExpandRecordColumn(Source, "Column1", {"ticket_id", "created_at", "updated_at", "group_stations", "assignee_stations", "reopens", "replies", "assignee_updated_at", "requester_updated_at", "status_updated_at", "initially_assigned_at", "assigned_at", "solved_at", "latest_comment_added_at", "reply_time_in_minutes", "first_resolution_time_in_minutes", "full_resolution_time_in_minutes", "agent_wait_time_in_minutes", "requester_wait_time_in_minutes", "on_hold_time_in_minutes"}, {"ticket_id", "created_at", "updated_at", "group_stations", "assignee_stations", "reopens", "replies", "assignee_updated_at", "requester_updated_at", "status_updated_at", "initially_assigned_at", "assigned_at", "solved_at", "latest_comment_added_at", "reply_time_in_minutes", "first_resolution_time_in_minutes", "full_resolution_time_in_minutes", "agent_wait_time_in_minutes", "requester_wait_time_in_minutes", "on_hold_time_in_minutes"}),
  #"Changed Type" = Table.TransformColumnTypes(#"Expanded Column1", {{"created_at", type datetime}, {"updated_at", type datetime}, {"assignee_updated_at", type datetime}, {"requester_updated_at", type datetime}, {"status_updated_at", type datetime}, {"initially_assigned_at", type datetime}, {"assigned_at", type datetime}, {"solved_at", type datetime}, {"latest_comment_added_at", type datetime}}),
  #"Extracted Date" = Table.TransformColumns(#"Changed Type",{{"latest_comment_added_at", DateTime.Date, type date}, {"solved_at", DateTime.Date, type date}, {"assigned_at", DateTime.Date, type date}, {"initially_assigned_at", DateTime.Date, type date}, {"status_updated_at", DateTime.Date, type date}, {"requester_updated_at", DateTime.Date, type date}, {"assignee_updated_at", DateTime.Date, type date}, {"updated_at", DateTime.Date, type date}, {"created_at", DateTime.Date, type date}}),
  #"Expanded reply_time_in_minutes" = Table.ExpandRecordColumn(#"Extracted Date", "reply_time_in_minutes", {"business"}, {"reply_time_in_minutes"}),
  #"Expanded first_resolution_time_in_minutes" = Table.ExpandRecordColumn(#"Expanded reply_time_in_minutes", "first_resolution_time_in_minutes", {"business"}, {"first_resolution_time_in_minutes"}),
  #"Expanded full_resolution_time_in_minutes" = Table.ExpandRecordColumn(#"Expanded first_resolution_time_in_minutes", "full_resolution_time_in_minutes", {"business"}, {"full_resolution_time_in_minutes"}),
  #"Expanded agent_wait_time_in_minutes" = Table.ExpandRecordColumn(#"Expanded full_resolution_time_in_minutes", "agent_wait_time_in_minutes", {"business"}, {"agent_wait_time_in_minutes"}),
  #"Expanded requester_wait_time_in_minutes" = Table.ExpandRecordColumn(#"Expanded agent_wait_time_in_minutes", "requester_wait_time_in_minutes", {"business"}, {"requester_wait_time_in_minutes"}),
  #"Expanded on_hold_time_in_minutes" = Table.ExpandRecordColumn(#"Expanded requester_wait_time_in_minutes", "on_hold_time_in_minutes", {"business"}, {"on_hold_time_in_minutes"}),
  #"Reordered Columns" = Table.ReorderColumns(#"Expanded on_hold_time_in_minutes", {"ticket_id", "created_at", "updated_at", "assignee_updated_at", "requester_updated_at", "status_updated_at", "initially_assigned_at", "assigned_at", "solved_at", "latest_comment_added_at", "reply_time_in_minutes", "first_resolution_time_in_minutes", "full_resolution_time_in_minutes", "agent_wait_time_in_minutes", "requester_wait_time_in_minutes", "on_hold_time_in_minutes", "group_stations", "assignee_stations", "reopens", "replies"}),
  #"Changed Type1" = Table.TransformColumnTypes(#"Reordered Columns", {{"reply_time_in_minutes", Int64.Type}, {"first_resolution_time_in_minutes", Int64.Type}, {"full_resolution_time_in_minutes", Int64.Type}, {"agent_wait_time_in_minutes", Int64.Type}, {"requester_wait_time_in_minutes", Int64.Type}, {"on_hold_time_in_minutes", Int64.Type}, {"group_stations", Int64.Type}, {"assignee_stations", Int64.Type}, {"reopens", Int64.Type}, {"replies", Int64.Type}}),
  #"Marked key columns" = Table.AddKey(#"Changed Type1", {"ticket_id"}, false)
in
  #"Marked key columns"