Why do I always get the same words when strengthening? Is it a bug?
Go Raibh Maith Agat!
It's partly how the site is designed. The algorithm is basically saying that's the only word of the skill you need to refresh. When you are getting one or two words to refresh, do you only have to translate about 2-10 sentences versus the normal twenty? Because that is what I see.
My recommendation is to do timed practice and then once you see a word repeated, you know you can stop practicing that skill and let the timer run out. That skill should still turn golden when the lesson is completed since you've already practiced the word.