Asked to save unmodified files

Hi,
I’m using Version: 5.4.4.2 (Build ID: 2524958677847fb3bb44820e40380acbe820f960) on Linux.
When I close some of my ods files, I’am always asked to save them even if I have done absolutely no modification. If I save them, the file size is slightly changed and the Linux “diff” command says the new saved file is different from the previous one.
What is wrong with these files?
Thanks

They contain charts, and there’s a bug with that.

Thanks for the comment. Didn’t know this bug yet. All I can says is this bug is confirmed!