When we upgrade the artifactory instance from the versions below 6.6 version to higher, the build migration fails if the build info.json file has properties with  in it.
The stack trace would be the following:
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.lang.String` out of START_ARRAY token
at [Source: (org.jfrog.storage.binstore.common.ReaderTrackingInputStream); line: 3, column: 17] (through reference chain: org.jfrog.build.api.Build["properties"]->java.util.Properties["testing"])
EDIT: this is not a regression, the fix only helped with a in-place upgrade, not with REST API build adds or with full system imports. Altering the bug to fix those cases.