I have three of the same HP Smart Tank 7305 with the same pproblem. After the printers were in sleep mode and i press the copy button, all lights start to blink. When i run hp-info i get unknown error. The printer then doesn't work anymore, it just continuously blinks and nothing works anymore until i plug the cord and restart it. Sometimes the same error happens without pressing the copy button. This is a problem because I automated a bunch of prints that need to work over the weekend.
The firmware and drivers are up to date.
Turning off doesn't work, i have to unplug it.
I don't think restoring to factory defaul will help, because this problem happens with all HP Smart Tank 7300 printers I have. One is brand new, just a month or two old.
I hope this is a known problem, it is easy to replicate, just wait for the printer to enter sleep mode, wake it up, then press the copy button.
Thanks for the help.