ME23N Search PO by Vendor not populating vendor field

We are having the following issue with the vendor search field not populating.

ME23N

Other PO

F4

Select the Vendor field, F4

Enter a search term or leave blank, enter

Double click a vendor from the results. (Even clicking on the Vendor number directly)

Instead of the vendor number being populated in the vendor field, it seems to take the last few characters from the city field.

I don't think we have any config that would have done this?

Seems it may have just started happening after our upgrade to ECC 6, EHP 6, SP12.

I tried to do some searches for this issue but couldn't find anything.