Docker 19 cacheing, authentication token with watchtower


I’m currently using watchtower to periodically check for updates and pull images from a container registry.
The registry (Amazon ECR) requires an authentication token, which is stored in docker/config.json.

I’ve recently updated to Docker 19.03 and after that, I discovered that watchtower fails to call the repository to check for updates. The reason for this is due to failed authentication.
After a reboot, the server authenticates successfully (maybe the cache is cleared) but after 12h the auth token is invalid and the call fails, even though config.json contains a new token.

This is working flawlessly in servers running Docker 18.09.
Is it possible that there has been any update in Docker 19.03 on how the caching is handled, and therefore new tokens are never fetched?
If so, is there any workaround for skipping this cache?