CV Tools Clock in - weird drift?

I have been trying out the CV tools Clock in device. It seems to work OK at first, but slightly drifts over the duration of the recording - the longer it records for the more drift is evident. There are a number of things I'm not sure I understand and would really appreciate some help.
1 - why is the drift linear? Is this affected by the buffer size? I have it at 128.
2 - why does CV tools add hundred of warp markers that don't match any transients?
3 - is there a way I can get it to sync to the transport i.e. the 1 2 3 4 corresponds to the 1 2 3 4 on the grid.
The best result I have had so far is my using clock in to work out the tempo then turning the device off and then slightly altering the recording afterwards with warp markers. This can't be the best way of doing it though.