Session reporting way off for some posts

Hello, 

One of my posts has had 3540 views in the last 30 days according to Google Analytics (matches Pinterest analytics). According to Grow it has gotten 373 views (I made sure the dates were the same on both platforms) - it's been like that for at least a week. 

What is also weird is that it's my number 2 post for traffic, and it shows as number 2 in Grow when I sort the posts by traffic (number 3 has over 2k pageviews). 

As far as I can tell, another post is also concerned. The rest doesn't match exactly but the range is small.

Thank you for your help,
Julie