AutoCAD Inventor :: Unable To Expand Assembly In Presentation (ipn)

We have the following problem / bug and i was wondering if others can reproduce it.

(IV2013, SP1.1)

When adding a new sub-assembly to an existing ipn, the newly added assembly doesn't have the + sign to expand it. (see image)

Steps:

1. create a part. (anything will do) - Part1
2. make an assembly and add Part1 a few times. - Assembly1
3. make another assembly and add Assembly1 a couple of times. - Assembly2
4. create a presentation file with Assembly2, add a tweak for good measure. - Assembly2.ipn
5. Save the ipn. (and any other unsaved files)
6. now go back to Assembly2 and add another instance of Assembly1.
7. look at the presentation again, if it's the same as our situation there shouldn't be a + next to the newly added instance.