It's not a good idea to reuse the spring washers, if they've been under tension for a while or if they've been affected by corrosion, most, if not all, of the spring force is gone.
The spring washers that bolt the transmission suspension mount to the chassis serve an important function, since in most Volkswagens where these spring washers are used, the entire engine is suspended from the transmission.
Don't try to save money on a set of spring washers, but install new ones and don't reuse your old, worn out washers.
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