You saw an error message to the effect of:
Error updating data, data too long for symbol
The database has certain length limits for various fields and for the plant symbol. We eventually plan on extending it. In the meantime, it just requires keeping plant file names short.
You might have a tree named Copy of Tree-Dcid-006, which is just too long. So of course the easy solution is to rename it to get rid of the "Copy of" prefix, and just give it a unique number. Note that the file should have two sister files – an SLD slide preview image, and an XML data file – both of which you should also rename to match the change to the DWG name.