Unable to handle gosumdb requests for certain modules

go get is failing for some modules for customers after moving to 6.17

Steps to reproduce:
1. Create a virtual repository that includes the default remote go modules repository (gocenter)
2. On go 1.13, run a `go get github.com/Shopify/sarama@v1.25.0`
3. Errors will be observed.

Note:
If GOPROXY is set to https://gocenter.io, then go get is successful.

The customer started seeing this error after upgrading to 6.17.

Logs from customer -

verifying github.com/Shopify/sarama@v1.25.0: github.com/Shopify/sarama@v1.25.0: initializing sumweb.Conn: checking tree#712325: reading https://<some artifactory repo>/sumdb/sum.golang.org/tile/8/1/010.p/222: 404 Not Found
1:56
ran a couple times, got similar error for different urls and its finally stabilized on this:
go get -v github.com/Shopify/sarama
verifying github.com/google/go-cmp@v0.3.0/go.mod: github.com/google/go-cmp@v0.3.0/go.mod: TileReader returned bad result slice (tile/8/0/039 len=4096, want 8192)

after go clean -modcache it gives that first error again