If I send myself a file containing an image, I can right click an upload image. If I then save this file and reopen it the images are gone again.
What OS (and version) are you on?
@DavidWilmot, Also please try to help others here as you get help yourself, by making your question titles, titles, and include the details below. … So, as with all databases, as ask.libreoffice.org is just another database of information, others can search for a problem an hope to find an answer that someone else had before them. If you put huge amounts of text with many common words in your subject the search doesn’t work very well. Try: “Images gone with 5.2 upgrade”
Changing release will not affect existing .odt files.
Assume a file is fred.odt. Rename it to fred.zip. Double click fred.zip. Your images should be in the folder \Pictures.
Are you displaying them (this could have changed when you upgraded)? Tools > Options > Writer > View > tick Display graphics.