Why does the Next Status is set to blank in F4311 - this happens sometimes.

I seen couple POs with NExt status with blank the Program ID shows EP4312. One PO had one line and 000 to 004 Order suffix and the 000 suffix had a blank Next status.

2nd PO has 2 linesand both lines had order suffix 000 however both Program ID was EP4312 and only the 1st line had NExt stsus code as blank the line 2 was fine.