API connections in two steps no longer working

Hi,

I've several reports that connect to third party sources using private API's - as they have daily exports of the current data, I wrote queries to connect to the API to get the list of exports, then take that answer and put it in to another version of the same API, giving me the information from the correct export.

All of them have stopped working with the Jan 2021 update of report server - they will refresh correctly in the desktop but scheduled refreshes fail with the generic error:

 COM error: Microsoft.PowerBI.ReportServer.ASEngineManagedRoot, The given data source kind is not supported. Data source kind: UnknownCallsite..

 One of the reports is still refreshing but when I copy that query into a new blank report, that fails it's test scheduled refresh with the same error.

Does anyone know why this is or if there is a work around?

My queries all work roughly the same way (I have put the second call in a calculated column/function, as well)

let
Source = Json.Document(Web.Contents("[API LINK]/[source identifier]/exports?api_token=[TOKEN]&api_token_secret=[SECRET]")),
Source1 = Source{1},
#"Converted to Table" = Record.ToTable(Source1),
Value1 = #"Converted to Table"{11}[Value], //this value is the api link for the latest export
Source2 = Csv.Document(Web.Contents(Value1 & "?api_token=[TOKEN]" & "&api_token_secret=[SECRET]"),[Delimiter=","]),
#"Promoted Headers" = Table.PromoteHeaders(Source2, [PromoteAllScalars=true]),

...[REST OF QUERY]...