Rank Math is deleting all the images alt tag value from backend for custom field

Hi,

I am using custom theme.

The issue is, I have uploaded the image from backend by custom field(Not ACF) on the home page, after uploading the image, when I did inspect element on the preview image, I did not see any alt tag value, and for that ‘Add an image with your Focus Keyword as alt text.’ this is marked as ‘red’ cross (https://paste.pics/RB4FU). But when I deactivated the ‘Rank Math SEO’ then I can see all the images alt tag value.

Why Rank Math deleting all the images alt tag value?

See the screenshots here:
https://paste.pics/RAXFQ
https://paste.pics/RAXI9
https://paste.pics/RB4FU

Anybody help me?

Thanks