Key feels like a sponge

One of my keys started to feel a little bit like a sponge and less clicky than the other keys (sorry for the wierd descrption XD). It is the tab key which I frequently use. It still works, but requires much more force to press.
Does anyone have an explanation and a possible fix for this?
For kontext the keyboard is about 1.5 years old.

Check if there is not food or something else stuck inside…

Okay it seems fine now, maybe it recovers after pressing it multiple times.