Did JTAC give you a PR number that the bug was covered under?
Typically this type of behavior will be a software bug. These are tracked by Juniper as PR (problem reports) each given a number and then a specific version of Junos has the fix that that particular bug.
So if JTAC has identified the bug affecting your traffic and saying you need to upgrade to a specific version of Junos this is where that but is fixed. Ask them for the PR number and bug description if you are not sure the upgrade will fix the issue.