This issue has been resolved in the Video Timing Controller v4.0 and later.
There is a discrepancy between the documentation and the core functionality.
To perform a soft reset, the user only needs to write 0x0000000A.
This will cause the core to reset.
It will then automatically recover from this.
Please see (Xilinx Answer 32754) for a detailed list of LogiCORE Video Timing Controller Release Notes and Known Issues.