panic: AddSumEvent failed the channel is closed or full

I am trying to copy some VHDs from one container to another in the same storage account.

It keeps failing at random stages with the below:

C:\Temp>.\Blobporter.exe -f "[https://storage.blob.core.windows.net/archived-vms"](https://jhpuksarchive.blob.core.windows.net/archived-vms%22) -c archived-virtual-machines -t blob-blockblob -b 90MB -h 1
BlobPorter
Copyright (c) Microsoft Corporation.
Version: 0.6.20
---------------

Files to Transfer (blob-blockblob) :
16 files. Total size:4762044997632
--> 12 % [|||......................] Committed Count: 0 Buffer Level: 100%panic: AddSumEvent failed the channel is closed or full

goroutine 243 [running]:
github.com/Azure/blobporter/internal.(*eventSink).AddSumEvent(0xc00003c1c0, 0x2, 0x75d919, 0xc, 0x0, 0x0, 0x3ff0000000000000)
/home/travis/gopath/src/github.com/Azure/blobporter/internal/eventsink.go:232 +0x1cb
github.com/Azure/blobporter/transfer.(*Worker).startWorker(0xc00020cc90, 0x7ba360, 0xc0002ba0a0)
/home/travis/gopath/src/github.com/Azure/blobporter/transfer/worker.go:89 +0x80e
created by github.com/Azure/blobporter/transfer.(*Transfer).startWorkersAndCommitters
/home/travis/gopath/src/github.com/Azure/blobporter/transfer/transfer.go:376 +0xae