There is a fatal flaw in the design for Symbols. There currently is no way to recover edited symbols from an older version of a file by pasting them over to a new file. This means that symbols that were edited with the syncing button turned off, are copied in as the regular version of the symbol.
Steps to reproduce
Create an ellipse and turn it into a pie
Convert this ellipse into a symbol
Save the file
Create a copy of the file from step 3
Place another symbol in the file
Disable symbol syncing
Change the angles of the pie for the symbol in step 5 (and optionally scale the symbol down for recognisability)
Copy the edited symbol and paste it into the original file (which didn't have the edited symbol).
Notice how the symbol is brought in and disregards any changes to it
2023-01-11 16-41-21.mp4