Any changes made to: 'Customizer > Project Thumbnails > Project Title > Space between Title and Image' are not being applied to existing thumbnails (at least on my site).
However, the changes do apply if a new thumbnail is added to the grid.
Here's my site (staging, in progress): http://beige.temp312.kinsta.cloud
The space of the last thumbnail (Adidas Runtastic) shows the new settings. But all other spaces have not changed.
Please have a look into this when you get a chance.