Compiler errors related to Player version when global swc caching turned on

Setup an SDK developer environment and sync to the latest branch.

I occasionally get a bunch of compiler errors similar to this one:

1119: Access of possibly undefined property BACK through a reference with static type Class. MobileApplication.as /mobilecomponents/src/spark/components line 512 Flex Problem

These errors usually go away when I perform a project clean. However, this time they are no longer going away. Could FB be holding on to an older version of the Player swcs? I've been seeing this problem intermittently for a few weeks now.

Turning off the global swc caching solves this problem.