That's not what double dipping means.

In this case, I presume they're taxed on their continued employment and so they're still paying into the pension they're receiving benefits on? I don't see a problem if that's the case. They contributed to the pension with an agreed payment date and followed the process correctly. I can understand how you feel that it's unfair, but I really don't see a problem unless they stop paying into the pension or stop paying taxes on their continued employment.

The double-dipping unfairness is mostly perceived when there is high unemployment in youth, and we're allowing, via tax rules, for retirement aged persons to have decent returns on their work. They get a living-rate pension AND a job.

Like others note, UBI is a fair solution. Let's have everyone, regardless of age, be able to have a baseline. Then allow extra income form those who enjoy, or value, additional work and income.