Field Modification Auto complete rule for FTE- Assignment Category rule not working as expected

Summary:

We have a Field modification type auto-complete rule set-up for defaulting Assignment Category based on FTE and working hours. But it is defaulting only when the FTE value is being changed manually in RUI which is in a different section than the Assignment category field.

Content (required):

Expected behavior- When the working hours are changed the FTE changes automatically and the Assignment category should update automatically based on the FTE without having to navigate to that separate section and coming back.

Actual behavior- FTE gets updated automatically(delivered system behavior) when the working hours are changed, but the assignment category does not get updated even after navigating to that section in the RUI and coming back to the Position details section. Assignment Category field gets updated only when the FTE is changed manually which causes an indifference in the working hours and FTE.