I get the following dialog:
Error saving the document RealTempLogCorsairOnly:
Wrong parameter.
The operation was started under an invalid parameter.I have accidentally found a solution: just make sure that your graph is not selected when you’re saving the document. Select any cell instead.
This helped me. thanks 
Worked for me as well!!
What a crazy bug/feature
This just helped me immensely. This is awful behavior for someone who infrequently uses LO. If LO has special behavior based on what is presently selected (like saving only a portion of the spreadsheet), it should be entirely more obvious that is what is happening. If there’s no special behavior, this is just a big ugly bug IMHO.
The error message does not indicate a problem with the file containing a chart (graph) but rather a filename / network problem. Which operating system and LO version are you running? Are you saving to a network location? Was the filename “RealTempLogCorsairOnly” or “RealTempLogCorsairOnly.ods” or “RealTempLogCorsairOnly.xls” i.e., did it have an extension?
most recent version of LO
I was saving it under the default file type (odc i think)
In any event, it would save the spreadsheet ok, just not a spreadsheet with a graph on it.
I did notice that when I checked the box saying ‘automatic filename extension’ the problem went away.
tnx for your reply but all is ok now.