Walk Behind Lawn Mowers

I bought a Husqvarna XT 722FE prod # 96143006104 walk-behind mower a few weeks back. the left front wheel won't stay locked at the correct height; it slips out and has to be reset several times during the cutting. the cover that's inside the wheel appears to be loose as well. Should that have been tighted? Also, the engine makes a high chirping sound as it's cutting. Any help would be appreciated.