Problems with this particular scope !! - Tasco 10-40x50 Target / Varmint Rifle Scope

Purchased this scope for small bore bench rest (.22LR) worked fine for the first 12 months but now windage adjustment is virtually non existent unless given a good tap but then it can finish up anywhere! Can't complain about the price but price isn't every thing when it doesn't do what it was bought for!!! Scope is about 2 years old now but hasn't been fitted to my target rifle for around 6 months.