A caption is currently recognized as simply text with the structure "{label} {number} {description}" (like "Figure 1 Pandas on the forest") immediately after a captionalizable element (an image, table or equation). So if there happens to be some text with the structure mentioned immediately after a captionalizable element, it may be incorrectly recongnized as a caption. There are plans to add better checks that are independent of text structure.
When you update your captions or insert a new list, old lists are not automatically updated. This follows the behavior of Google Docs Table of Contents, but it is important to remember that Caption Manager lists do not have their own refresh button/mechanism. Therefore, it is recommended to manually delete old lists after creating one.