Unable to Change Selections on Event Registration, Error: "Expected one Contribution but found 0"
This seems to be resolved with the commit from March 2, 2018 here: https://github.com/civicrm/civicrm-core/commit/b512c92fe8bbe9a8ef71ae9ba5adbcfe7500d81c 

With that change applied, we longer receive the error and everything works as expected.