[movies]

Well, I looked this up and it does seem that the reaction goes through 4 with the retro-Dieckmann leading to the cycloheptane.  Not much info on why you get a mono-acid though.  Very interesting transformation and an unusual one to think about retrosynthetically.  I like it!

Also, I fixed the link in my post above, sorry about that!

[Heory]

It's reasonable that one ester stayed intact due to higher resonance stability over that of the other ester group.

[movies]

That's a possibility, but these are pretty poor conditions for ester hydrolysis, so I suspect there is something more going on.

[Heory]

I think the hydrolysis reaction is quite rational in presence of 1 equ. of DBU.

[movies]

The DBU isn't the problem, it's the one equiv of water giving apparently complete selectivity for hydrolysis of one of the esters.

I dug up another paper that talks about the hydrolysis a little more and it seems that it is often only partial hydrolysis under the reaction conditions and the complete cleavage of the unconjugated ester only occurs during the workup.  The workup is also necessary in some cases to complete the elimination of the beta-hydroxy group.