Solution
The issue with PXIe-6614 and PXIe-6612 is an expected behavior due to a routing problem. Although the counter channels are written sequentially from ctr0 to ctr7, they are not started in sequence causing some routes of counter 3 to be occupied by another counter, resulting in the error.
To resolve this, it is recommended to reserve the counter tasks sequentially. Once reserved, the tasks can be started parallelly without triggering this error. Refer to the picture below on how to reserve the counter task:
