what the meaning fo this Warning

what the meaning fo this message -
“Warning Can’t save E:/Work_Projects/unreal/…/Content/02_Materials/Parent/Parent_M/Floor.uasset: Graph is linked to external private object (unknown culprit) (unknown property ref)”

thank’s for the help.

thank you for your answer.
is ther a clean up function?
what you mean by - “references something that doesn’t exist”?
the model and the matierial exists.
i am a beginer. so if you can direct me. i’ll be grateful.

whenever you move an asset from one folder into another, it often moves most of the asset, and leaves behind a redirector file, so anything that references that asset is still connected. right clicking on a folder gives you the option to fix up redirectors in folder, and this should be used on any folders that you moved assets out of.

but, if you change the name of a folder or asset in windows file browser, instead of renaming in ue4, it will not create redirector files, so all the references to that object that got renamed will break.

i tried the first part of your answer. it didn’t help.
the last part i didn’t understand,
the message appeared when i did a material. it not attachment to an object.
the material image attachment!

i have had this error many times before, its kind of random and vague. sometimes its easy to track down the problem and replace a reference, or rename a folder, other times its due to some kind of circular dependencies or just a corrupt file of some kind, so in your case, it might be easier to remake the material from scratch.

Scott. thank you for you time and effort to help me.
i found what was my problem. but i still don’t understand, why unreal act that way.
i copy paste the uv section from one of the MF material to the blend, that was the reason, even the comment area caused the problem,
again thank’s.