The following two issues are possible.

①You must either remove the crystals that have formed and clogged up the end of the buret tip or replace the buret tip.

【Please be careful】
When cleaning, if you change the shape of the tip, the liquid may stop dripping out normally.
Furthermore, a tube is press-fitted to the end of the buret tip and it may come out of place, so please take caution.

②Fixing the buret syringe in place.
Please remove the syringe from the buret head and confirm the vertical motion with a push rod.
If it is not working normally it will be necessary to replace the syringe.