This is a common problem with older, inexpensive scopes. The internal lubricant loses their solvents and become gummy. I have found that if you can get them to move, you will be alright. You might try a little heat from a hair drier but I would not go any hotter than this.
Just go for warm, not hot !!
I have only seen this problem on much older, cheap scopes that have sat too long, on one setting...
Be Safe !!!