I don't know about Shimano baitcasters but IMO Shimano spinning reels are some of the best on the market. I've been a spin fisherman for a long time. Still love my Abu-Garcias and still have several of the 2nd generation Cardinals and still use them a lot but my first choice are Shimano's. I admit I'm a little spoiled as I save up and buy the high end ones (there is no substitute for a Stella!) but even their more affordable models I have are clearing superior to most others in their class.
As far as your problem, you clearing have a mechanical problem with the reel. You need to break it down and take a look. Hopefully you got the manual when you bought the reel. I couldn't find it online but I didn't look real hard. If you think it's worth it you might want to consider sending it to a professional repair shop.