Have you read this thread?
Take a look at the video and read through it, see if it matches your issue.
Adobe did release a Flash CC update specifically trying to fix this issue. Also make sure what you have your brush settings configured to isn't to straighten lines. As Flash turns your lines into shapes, internally it has to decide if you meant a very slight curve or a straight line. If the curve is too slight, it will be converted to a straight line.
Can you give some details on the hardware you have, Wacom type, driver version, OS, computer, etc. Also have you tried any other applications (Illustrator, Photoshop, Fireworks, etc) and witnessed similar results?
Hi Dualech, flash CS6 is available to all CC users and you can down this from creative.adobe.com. Can you check if you see the same problem with CS6 with the same set of drivers/devices and on on the same system where you noticed the issue with CC.
Computer: ASUS X551 Notebook
CPU: Intel Celeron 1007U 1.50GHz 1.5GHz
4 Gigs of RAM
Wacom Intuos S, (The brush tool is slow in CC, generally, the intuos works fine) brand new drivers
OS: Windows 8 64x
I have not yet tried any other Adobe products as of yet, gonna see about CS6.