I have checked firstly with them – they said it is related to theme :/
Their answer:
“Our development team checked it further and found that the issue is related to post-thumbnails key which is used by the theme and is stored in database as 150px images.
This can be due to various reasons and one of them can be an old plugin which was installed which made such a change in database. It will require further debugging into theme code and database to fix the same.”
