Custom Symbol: Error on requesting bars series

[Joerg]

Hello,

under https://ninjatrader.com/support/helpGuides/nt8/NT%20HelpGuide%20English.html?performance_tips2.ht m it is mentioned: "Workspaces which have a single or fewer number of instruments are unable to take advantage of multi-core processors. For example, having 30 charts with the same instrument will not perform as well as 30 charts of different instruments on a multi-core processor."
Therefore I like to have different symbols for NQ futures in order to increase the overall performance of NT when having multiple NQ charts open. I know that these then will not behave as one synchronised symbol anymore regarding any global variable (like orders / positions etc.).

I added a custom symbol named "NQA" with the same symbol settings + mappings (including the rollover data for 09-24) as the original NQ symbol. With that I can open a chart for NQA 09-24 which then plots bars for realtime data but it is not able to load any backfill-data for the time before the chart has been opened. The error message which pops up is:

Error on requesting bars series: "Unknown instrument NQA 09-24"

Since the mapping is working for realtime data what can I do to also get backfill data for such a custom symbol?

Many thanks in advance