I am having this problem also , but only on saved LayOut files where I have exported a one page PDF. I insert SU files, move/copy and use Scenes to select or change images. I sometimes use copy/past from the right click, or Cont C/Cont V to copy a viewport to another page. I double click on images and enlarge/move all the time. I am not technically oriented, so do not know how to use other options mentioned above, like render.
I have been creating LO documents for a couple years now with no problem, and exporting PDFs, including on these same project files with no problem, same drawings, until I exported only one page of the file as a PDF. This last time, after having to go back to a past version and re-do several pages, I saved several copies of my LayOut file, and marked one as the file I would export the one page PDF, and yup, that one is the one that opened the next day with the exact same corruption problem - images gone, text box lines all going to upper left corner, remaining text on page with pink background, and the yellow triangle. The saved files, not exported from, were fine (thankfully). I am only getting this problem on pages of my LO file that are line drawings, created on SU as flat red/green drawings , not the color images of 3D models. .