Hello forum,
I’m using acf pro v5.7.11 on wp v5.0.3.
I’m having an issue using acf location with Post Template.
It works fine with Page templates, but don’t with Post Template.
I’ve found a fix on the forum in this thread : https://support.advancedcustomfields.com/forums/topic/custom-post-type-page-template/
the fix : https://github.com/joelstransky/Advanced-Custom-Fields-Post-Templates/blob/master/functions.php
but it’s buggy, i get this php error while editing posts : Notice: Undefined index: page_template
on this line : $page_template = $options[‘page_template’];
here is an image showing what I got on acf’s location on Page Template, Post Template, and Post Template with the fix.

to me it seems to be a problem with listing the templates in acf location Post Template.
anyone having the same issue ?
5.7.12 was released soon after 5.7.11, and includes several bug fixes. Have you tried 5.7.12?
https://www.advancedcustomfields.com/blog/acf-5-7-12-release/