I did have trouble with them sticking in the frame slide mount on one bike, but I rubbed down the frame slide front and rear inner faces with some fine emery cloth and used some hard wax polish afterwards whch seemed to permanently cure the problem.
You may need a thin flat piece of wood to wrap the emery around to work inside the narrow grooves when rubbing down.
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One battery I bought was slightly swollen and always stuck as I slid it down onto the base plate. I only realised it was swollen when I picked it up one time and the sides moved in my hand. One email to Ching sorted it out, Have you checked that the plastic outer casing is fitted correcty?