I’ve run into this same issue. Data being imported from post object from my custom post type is not being set. I tried ringit’s solution but no luck. I’ve tried mutliple different ways and I am using the most up to date version of WP Allimport.
The data for the post object import contains the slug of the post (not the post id even though I have it set, i am guessing this was the fix Soflyy applied) but it still doesn’t work for my custom post type
Any ideas?