problems with audio and pdf in introduction #1, #2 and #3

[thrhymes]

#1 - no pdf
#2 - no audio, no pdf
#3 - no audio, no pdf

when starting the audio-player it starts buffering, then changing to "error opening file"

when loading the pdf, a blank page is displayed.

[hyunwoo]

thrhymes,

Thank you for reporting this. We're working on it to fix it! Thank you for your patience!