Send multiple http bulk requests with new_visit=1 cause strange order

I have save some bulk requests in my local file, with the first requests has param new_visit=1, and each have cdt time, which looks like as follows.

file 1:

{“requests”: [
“token_auth”: “…”}

file 2:

{“requests”: [
“token_auth”: “…”}

time1<tim2<…<time6, and every time is within 30min

if I post file1, then file2, the websites/database showed:
visit 2 : action 4, action5, action6
visit 1 : action 1, action2, action3

if I post file2, then file1, the websites/database showed:
visit 1 : action2, action3, action 4, action5, action6
visit 2 : action 1,

I want to know what’s the reason? why in situation2, action2&3 are not followed with action1?

Can I force them in one visit?