I use a bell hammer sprayer and recently the liquid has stopped coming out. If I shake the can more, it comes out only then. But this is only temporary and does not last.

We cannot give you an accurate answer because we cannot actually see the actual product, but the inability to dispense the liquid all the way to the end can occur with all aerosols, including our products and those of other manufacturers. A large percentage of this is due to the fact that the product is used upside down for a long time. (Of course, aerosol failure is possible at a rate of about one in several hundred thousand.)
When the aerosol button is positioned below the center of the body, such as when the product is often applied to a low position, the gas spurts out and the amount of liquid released is small, resulting in only the gas spurting out and the product not being used to the end.
When using aerosol products under downward conditions, shake the can well before spraying, then shake it again before spraying, and repeat the process until the product is fully used.