I will check to see if I have a block protector, but think that this may have been caused by user error - restart attempts before flywheel has come to a rest. It's happened a few times - if you can believe because in the early days my key chain was a bit long and I inadvertently turned off the ignition while driving and then wasn't thinking and turned the key to start rather than run.
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(Less time searching, more time wrenching & driving)