Why are my Macbook Pro 2016 key caps falling off? How to avoid this?

Hi.

After getting the Macbook Pro 2016 top case replaced about 12 month ago (reason: key pressed once but multiple times fired), the key caps have started falling off. Last month it was "S" and now it is "F". In both cases the butterfly mechanism and the key cap clips look perfectly fine (cf. photo). The "S" was replaced at an Apple Store and for the "F" I have an appointment this Wednesday. (After re-attaching the key cap it will simply fall off again, the clip is not holding anymore)

But how can I avoid that in four weeks from now the next key cap falls off?

All the best.

Jens