Id guess if you remove the tap body, you will find that the washer is worn and flat. which lets the spindle wind down further than it should. That exposes too much of the spindle 'O'ring and lets water get into the spindle and trapped behind the 'O' ring when you open the tap. You can not compress water, so the spindle and jumper will not rise.
Take the circlip off the top of the tap body, wind out the spindle, change the 'O' ring and washer, and refit.
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