According to the BB-Code cache, you have DIV with "Is this a Wiki link BB-Code" = "Yes" in the Syntax Manager. VaultWiki doesn't want to put a link inside another link (not valid HTML), and since links are inline-level elements, it doesn't want to put the image in a block-level container with borders (that would also be invalid HTML).
Currently this is all functioning as designed. Since you have told VaultWiki that the containing DIV is a link and it knows links are inline, it uses the behavior for inline images. The caption will show as alt text if you hover over the image.
If you would like to have images function as expected in a DIV, and also have DIV function as a block-level element like it does in HTML, then you should turn off the setting "Is this a Wiki link BB-Code" for DIV.