Assuming that you have everything attached to a box or container so that everything is all grouped and acts as just one element.
Try the following:
- Open the relevant page in edit mode
- Select the page elements that are being collapsed/expanded
- Cut the elements (with Ctrl/cmd + X)
- By clicking and dragging the mouse, select the white space to locate any (hidden) elements that might affect the footer position. Then either remove or re-position them.
- Drag the footer upwards
- Place the element back by pasting it (Ctrl/CMD + V)
Have a look at this previous forum post too.
https://www.wix.com/corvid/forum/main/comment/5af45d2eadd7000030a314ee
Plus make sure that you read this page too.
https://support.wix.com/en/article/corvid-how-page-layout-is-affected-when-elements-change-size