Can you please manually specify a non-generic name for the downloaded source file?
Generic name like v0.3.3.tar.gz is likely to conflict with other packages that also wrongly use generic names, if one has set $SRCDEST, since then everything is downloaded into a single directory.
Try things like source=("${pkgname}.${pkgver}.tar.gz::https://github.com/hVitozz/cppAlsaVolume/archive/v${pkgver}.tar.gz") to achieve this.
Regards!
