so it does finish eventually; 2.5 minutes for worker op 1 IsValidPath and 1.5 minutes for worker op 7 AddToStore:

Dec 04 12:30:06 performing daemon worker op: 1
Dec 04 12:30:06 using cache entry '{"ingestionMethod":0,"name":"source","type":"file","url":"https://github.com/nixos/nixpkgs/archive/418468ac9527e799809c900eda37cbff999199b6.tar.gz"}' -> '{"etag":"W/\"5cd48868382e96938f2a04bff191018f8b59407d9ae34339c558b716c665372e\"","url":"https://codeload.github.com/NixOS/nixpkgs/tar.gz/418468ac9527e799809c900eda37cbff999199b6"}', '/nix/store/6zx3brkqjsnr53b2p3fdn2k44q6pyj25-source'
Dec 04 12:32:33 finished performing daemon worker op: 1
Dec 04 12:32:33 performing daemon worker op: 7
Dec 04 12:33:58 finished performing daemon worker op: 7