Could you please clarify the action of the LOWPRIO bit in the SEQA_CTRL register.
The manual says that it sets the priority for sequence A.
In low priority mode, any SEQB trigger is ignored - thus SEQA has higher priority.
In high priority mode, the SEQB trigger interrupts the SEQA sequence, and the SEQA sequence has to wait until the SEQB sequence is completed before it can resume - thus SEQA has lower priority.
This seems completely contradictory to the description.