The common reasons for the plugging of the solder paste are as follows:
1: the stencils has not been polished.
2: the thickness of steel sheet is unreasonable, 0.1MM is better than 0.12MM.
3:PCB positioning PIN is not smooth, so it is recommended to make tin stamping fixture.
4: there is a gap between the stencils and the PCB plate.
5: check whether the scraper is properly installed. Is there any reverse problem?