Vent Selection Difficult To Turn

[Norwood-er]

Howdy all, I am new on here. I purchased a 2005 Silverado WT Non-AC 4.6L MT back in May of this year and shortly after I have a difficult time rotating the vent selection knob on the climate control. It became so difficult to rotate the vent selection knob that I actually cracked the knob and now have to use a vise grip locked onto the knob shaft inside the climate control. Even with the extra leverage from the vise grip it is still difficult to select vents. Has anyone ever had this issue? I have taken the dash apart before and have not seen any obstructions that would cause this. Any insight would be appreciated. The only info I can find online is for AC equipped trucks. Thanks!