The code checking for enough bars on all series should be at your OnBarUpdate() start.
Have you tried printing how many bars are actually processed then for the combined test and have compared the actual trades you see?
The difference could be also due to simply processing fewer trades / bars, as one series would be for example available only a few bars later - NT would then call OnBarUpdate only after all series had met their BarsRequired, so would be important to compare the trades you get on a limited set of symbols / series to better understand.

Comment