Paid developers ask unpaid volunteers to do work

The more your product and code is used by people and companies around the world, the more people at said companies will come back and demand answers or bugfixes (often rudely). Sometimes mentioning or hinting how they are short on time, that they need their product fixed as soon as possible or similar.
In many cases these persons have the problem at their daytime paid jobs, while you work on your project on your spare time. The paid developer asks the unpaid one for immediate help.
This is not something that you can easily change. If you are the one asking the question: be aware and be grateful that people are actually helping you out. If possible, check if you can pay for support or maybe make your company a sponsor of the project as a show of your good will.