I have observed this issue related to regeneration of cancelled freight units in S/4HANA TM.
Whenever a freight unit is cancelled by the user, in the UI, a message "TRIGGER BUILD_FUS set for later processing" appears. The FU is not re-generated automatically and needs a change to be made in Sales/Delivery to initiate a new freight unit generation.
Has anyone handled it using any correction or BG program which can regenerate FU's immediately upon cancellation?
It worked that way with standalone TM as much as I recall.