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From time to time, a volunteer in a position of ongoing responsibility (e.g., patch manager, translation manager, etc.) will become unable to perform the duties of the position. It may be because the job turned out to be more work than he anticipated, or it may be due to completely external factors: marriage, a new baby, a new employer, or whatever.
When a volunteer gets swamped like this, he usually doesn't notice it right away. It happens by slow degrees, and there's no point at which he consciously realizes that he can no longer fulfill the duties of the role. Instead, the rest of the project just doesn't hear much from him for a while. Then there will suddenly be a flurry of activity, as he feels guilty for neglecting the project for so long and sets aside a night to catch up. Then you won't hear from him for a while longer, and then there might or might not be another flurry. But there's rarely an unsolicited formal resignation. The volunteer was doing the job in his spare time, so resigning would mean openly acknowledging to himself that his spare time is permanently reduced. People are often reluctant to do that.