Woocommerce image swatches

Hi everyone,
I’m having a problem with variation swatches on Woocommerce product pages. I’m using image swatches to display the colors, I uploaded the images for each variation but a few of the pruduct pages text appears instead of the colors (e.g. I uploaded an image for black but the text “Black” appears instead of the image). Other product pages do not have this problem? What am I doing wrong?