The master input for the unsorted Joiner transformation <transformation name> cannot be partitioned because the Joiner transformation is not a partition point.
You partitioned the master pipeline without adding a partition point at the unsorted Joiner transformation. This can cause input rows from the same key value to be routed to different partitions.
Add a hash auto-keys partition point at the Joiner transformation to ensure data of the same key value is routed to the same partition.