There is a bug in Adobe CC 2015 version 13.5. You will get this bug if you use GBDeflicker4 along with Warp Stabilizer.
Other plugin/effect combinations raise this bug too. Adobe has promised to fix this bug in the next CC 2015 release (Version 13.5.1) expected in mid July 2015.
It may also occur if you use time remapping or reverse time in combination with GBDeflicker4. The solution is apply GBDeflicker4 and render to a new composition. Then apply your time remapping to the new composition.