This happened to me twice now: I've started a batch operation (mesh generation) but remembered I wanted to change something so I immediately try to cancel the batch operation before it could get started properly.
The dialog remains in view and the loading bar and time continues but nothing is actually done so far I can tell. I can click on pause but it does not do anything. I can click cancel and it gives me a warning like it normally does but regardless of what I click nothing happens and the dialog box remains open.
I let this sit for a while but it seems to be in a loop. I finally have to force quit photoscan (standard)
The nasty part is that my file is now corrupt.
Nothing what can be solved by saving often but just something I still wanted to share. Perhaps somebody else can replicate this hang.