Split files when opening response in excel contains incremental response

Hi, 

I have about 8000 responses on my form, when i open the response in excel, the file is being split into 6 parts, however each subsequent part being downloaded from forms seem to also contain records from the previous part instead of the intended split 

e.g. 

part 1 : Records 1 to 1500

part 2 : Records 1 to 3000

part 3 : Records 1 to 4500

Intended behavior : 

Part 1 : Records 1 to 1500 

Part 2 : Records 1501 to 3000

Part 3 : Records 3001 to 4500

Thanks