You should submit the question to the factory for removing the pivot of leaf clamp with the insertion a small spacer that would allow thick leaves taken  in. An elastic ribbon may hold the clamp, but under drought most cams open stomata at nightr

 thanks Guideo Bongi,  Problem is not clamp, leaves are small to to be taken in the clamp but due to much moisture content it cant be equlibrate for next reading 

Are you sure that the leaves do not get squashed? (see Guido Bongi's comment). That might soak the seal and so it is difficult to dry.  Otherwise I would expect that leaving the chamber open for a few minutes, and perhaps fanning it to move the air around, should allow it to equilibrate with the atmosphere.