Reason 1- It departs behind SBC-BWT Exp which itself departs just 5-6 mins before 20:00hrs (even though its dep is @ 19:35hrs cos of late arrvl of AJJ-SBC Pass/Loco attachment(this is usually done after 19:40hrs)). So, at times it departs late from SBC itself (dont trust NTES in this case)
Reason 2- All trains from SBC to BNC take atleast 12 mins + it needs to give way for YPR-HWH SF