Pretty hard to tell without more information. But, lets try something.
Are you using a standard "Automatic Row Processing (DML)" process to create the row? If yes, you see where you have Item Containing primary Key Column Value? For example P1_ID, well add that item name to the "Return Key Into Item" field. This will make the newly created row ID available to the page in order to fetch the next pk value.
But this is just a stab in the dark.
Try to replicate the issue in apex.oracle.com and the share developer credentials so that someone can check. Or explain what process is creating the row and what process may be running next. Code would help too.
I think it's odd that the row gets inserted. This is why I suspect the insert is successful and then the prev and next calculations for the PK are the ones failing.