This is a timing issue, so the more devices there are, the more likely it is to occur.
device1: create session
device2: create session
device1: app cache lock acquired.
download and cache.
app cache lock released.
device2: app cache lock acquired.
download and cache.
=> this process delete(rimraf) one cached by device1 previously.
app cache lock released.
device1: there is no app. install failed.
device2: success