The V5.6.171 version firmware is a beta version, with many features still under testing and not officially announced, so issues can be encountered.
Regarding the function you mentioned, we have identified some technical issues that prevent it from working properly on all computers. Therefore, we have decided to remove this feature in the V5.6.177 version.
For now, you'll need to use C1 to achieve a non-delay keyboard and mouse passthrough.