Problem description: The Post button disappears in Line/Header views in Edit vendor invoice form after switching the page view or other actions refreshing the form

Business impact: it’s very confusing for new or non-advanced system users to not always see the button in the header/line view. It’s not obvious or user-friendly design to have the buttons disappearing after a few clicks requiring users to change to the grid view that’s the only one that is not missing the Post button. Below is one of the scenarios, another one is when the screen s=is refreshed after an error occurred after posting, another one is to create an invoice via Invoice pool, the button is missing from the beginning.

Repro steps:
1. Go to a purchase order
2. Click Invoice > Generate > Invoice
The Post button is available – OK
You can switch between header and line view by clicking on the right top corner
And the Post button is visible OK.
3. Click on Options > Page options > Change view > Grid view
4. Click on Options > Page options > Change view > Live view
Issue: the Post button has disappeared
5. Click on Click on Options > Page options > Change view > Header view
Issue: the Post button is still not available.