TYPO3 Core

Looks like some custom extension and code is involved (Rs\Indivumed).
Can you provide more information? The complete stack trace?

I don't think this is an issue with TYPO3 itself, but with the extension in use.

Hello,

it´s not a problem of a extension. Same error occurs on just using typo3 core.

Object of class TYPO3\CMS\Core\Resource\FileReference could not be converted to string

in /usr/www/users/rsndev/typo3_sources/typo3_src-10.4.13/typo3/sysext/frontend/Classes/ContentObject/ContentObjectRenderer.php line 4454

And the error is not in text medie content elemenet. It occurs in Page-->Resources-->Media. And another strange behaviour: if first reference is a jpg and the second is a mp4 the error is gone. So it happens only if you place just one mp4 reference.

Hopefully someone is able to reproduce

I'm not aware of any place where TYPO3 outputs the pages.media field by default. It has to be something specific to your setup.
Can you share the corresponding Fluid part?
Probably the reference is used wrong.

The Problem occurs on any TYPO3. I have tried a clean fresh installtion, without any special fluid rendering

I found the problem. I have used this old code, which is obsolete, because opengraph-tags are already configured in seo-extension:

        og:image {
            attribute = property
            stdWrap.cObject = FILES
            stdWrap.cObject {
                references {
                    data = levelfield:-1, media, slide
                }
                maxItems = 1
                renderObj = COA
                renderObj {
                    10 = IMG_RESOURCE
                    10 {
                        file {
                            import.data = file:current:uid
                            treatIdAsReference = 1
                            width = 1280c
                            height = 720c
                        }
                        stdWrap {
                            typolink {
                                parameter.data = TSFE:lastImgResourceInfo|3
                                returnLast = url
                                forceAbsoluteUrl = 1
                            }
                        }
                    }
                }
            }
        }

So bug status could be changed to solved