the_post_thumbnail getting wrong base url

Hi all,
I’ve got a wordpress install that sets config variables based on the current url: if it’s the local dev version, or production.
I inherited the site from a developer who did local dev at dev.domain.com.
But i’ve set up my local dev to be localdev.domain.com

wp-config sets various vars including WP_HOME and WP_SITEURL. It sets these variables correctly, and they’re set correctly in the options table of the DB.

BUT, when images are called via the_post_thumbnail, wordpress is trying to load the images from the old dev address: dev.domain.com

I can’t find any hard coded instanced of dev.domain.com in the codebase.
What’s even stranger is when I load an older copy of the site, that has the same config file, and accesses the same database, it loads the images correctly.

That says to me that something in the codebase is calling the old dev url.

There are no caching plugins active that I can see.
Please help!