missing coverage when running karma with multiple different configs

I have 3 different configs in a project: 1) common code; 2) site a; 3) site b. When I run grunt karma:siteACoverage or grunt karma:siteBCoverage or grunt karma:commonCoverage a coverage report is generated for the correct site. When I run grunt karma it only generates a coverage report for common and then the other 2 reports are empty? I am not sure where to debug this or how?

Reproduce the issue with the three configurations using the reported grunt karma:siteACoverage, grunt karma:siteBCoverage, grunt karma:commonCoverage, and grunt karma commands. Start at the Karma coverage handling for multiple configurations; done means the combined run produces non-empty coverage reports for common, site A, and site B.

Written by the indexing model from the issue text.