Is anyone experiencing an unexpected error on creating purchase orders...?

it's too wide to make a guess, but you should figure which line is creating this, then you can focus on the same, last time it occurred to me because of some other script deployed on the record(I don't remember why ). You can check workflow and scripts on that record.

Thank you!. Its resolved, it was something with the form i have created a new custome form that solved the problem.