Hi! In my case the I realised that the principal reason of blocking was due to file extension: the file wav was blocking!!! When I started to use mp3 file I didn't observed anymore any blocking nor any delay.
About bluetooth, I'm using it too in my project...and even here I had problems! Currently I'm using a bluetooth module HC-05. When I had bluetooth and VS105 on the same arduino board , I observed loss of bluetooth communication when audio was playing. I suspect this is due to same addresses devices...I never solved this.
Anyway I resolved in another way using two arduino nano: the first manage the bluetooth communication, the second manages the audio with the VS105 shield. The first arduino serially communicate directly to the second through physical wires TX->RX
bye