API Error - Loading Contract Lines

Hi Experts,

I am new to contracts. While loading Contract lines from using a custom Request Set i am getting the below error

Service Line already exists for Contract Number K02-47462 with support program 2 RNMG MGT, bill to location 10687447, ship to location 10689472, and start and end dates as 01-SEP-16 and 30-SEP-16

Coverage Line record could not be created: Line Start Date is not during contract effectivity. Please enter a valid date.

:1

Coverage for Site with covered id 10710283 for contract number K02-47462 did not get created due to Coverage Line API error

I get this error only for one only when i am trying to load 2 months data at a time. When i tried to load 1 line data this does not happen.