For those with sleep problems, try this:

Open a Terminal window...

to check which mode is active, type in
pmset -g | grep hibernatemode

0=old style sleep, 3=new (save to disk style sleep)

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to change mode, type in
sudo pmset -a hibernatemode 0 (for old style)
or
sudo pmset -a hibernatemode 3 (for new style)

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Hope this all makes sense!