QlikView's task queue system can interfere with task chaining events, as well as fixed scheduled tasks.
It is possible to configure the queue mechanism to allow for prioritized tasks. Review the possibility of setting up a Distribution Group / QDS Publisher Group, which allows for a more granual configuration of what tasks are run where, and how they are to be priortized against the queue system.
More details on the queue system can be found in Tasks are not executed as expected and are shown in status Queued.
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CPU and Memory settings to prevent overload in QlikView Distribution Service (QDS)
QlikView Tasks are not executed as expected and are shown in status Queued