will be working vs going to be working=not interchangeable?

"There are two structures for the future progressive tense, both of which are usually interchangeable.

subject | auxiliary verb (will) | be | main verb + ing | object/complement
subject | be-verb | going to | be | main verb + ing | object/complement"

When would they be not interchangeable?

I for one need an example to get my head round that.

Rover

Quote:

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Originally Posted by Rover_KE

I for one need an example to get my head round that.

Rover

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I would have liked to listen to an example too. It's just an extract from the text about the future progressive tense. But it would not present an example when it's not interchangeable. I was kind of hoping that I would get a hint from native speakers.