Marketplace updates- Sometimes have to install twice
Installation and Configuration
In the case that I saw on a customers machine it stopped on jrStore which was down near the bottom of the list 'S'.
Thats why i guess the time it takes. If the execution of the php script was taking longer than the server settings allowed for it, it wouldnt finish.
but then the quicker individual updates would finish.
Its a guess, but seams plausable.
. Its funny because its soo true.