Cheapest possible may be the problem.
If it is cheapest chinese rubbish then you get what you pay for. These are the cheap ones often found in supermarkets or down the market.
I have used pens a lot, any resonalbe brand is worth the extra money. And the good brands are better value, they do last longer. Or so I have found.
I have also found the good ones can be recovered if you accidentally leave the lid off. By placing the lid back on, leave them tip down and leave for 24 hours.