[R-pkg-devel] Tarball can't be unpacked

[Dalgleish, James (NIH/NCI) [V]]

* using log directory 'd:/RCompile/CRANincoming/R-devel/CNVScope.Rcheck'
* using R Under development (unstable) (2019-10-10 r77275)
* using platform: x86_64-w64-mingw32 (64-bit)
* using session charset: ISO8859-1
* checking whether tarball can be unpacked ... ERROR
cannot unpack 'CNVScope_2.7.6.tar.gz'
* DONE
Status: 1 ERROR

I've submitted my package to win-builder, but just can't get it to check it. I've checked it locally and it passes with flying colors (no notes of any kind). I have used the package on my own machine to build from source. Is win-builder down? How can my tarball be broken? It works on my machine, so I can't imagine it's a broken tarball. Is there some compression flag I should change when building the package?