The issue was fixed in 2.1.3.125.
I might be wrong, but I don't think the issue, which arose in 2.1.3.120, was a C4 vs C5 issue. Until 2.1.3.125 was released, the advice from @bobbyD was to downgrade to a 2.1.2.x platform version. Off course, the fix in 2.1.3.125 makes that unnecessary.
