Hi there. My name is ***** ***** it would be my pleasure to help with your issue.
Its sounds like you've got a gasket on the inside of the lever that could possibly be rolled or bunched up in one spot. If that's the case then the only way to correct it would be to fully disasseble the front body portion of the camera and re-seat or replace the seal.
There is a second possibility that there is debris in the on/off mechanism that's causing the issue. There's something that you can try here as well. You will need an aerosol can of QD/electrical parts cleaner. Try giving it a short burst of this around the seal of the button while working it in the on and off position. If it seems to be getting better, then continue the process until you get it freed up.
Hope this helps. Let me know if there's anything else that I can do to assist you. Please don't forget to cick accept and leave a positive rating for me. Thanks and have a wonderful day!!!