String Trimmers

I exchanged one 128LD for another 128LD yesterday, and 2 out of 4 times when I tap the head on the ground, the quick release/detach button would seem to dislodge and make the lower portion of the shaft spin.  Is this something I can adjust or do I need to return it to exchange?  I can't duplicate the effect by turning it with my hand, it only seems to happen when I use the bump feed.

I did follow the instructions to a 'T', as I can't always afford new expensive toys all the time, and I want to take care of it, I even used Husqvarna's pre-mixed 50:1 fuel.

It should be fair to mention that I had a previous 128LD that I returned to Lowes to get this new one as it was missing the pre-installed bolt off the shaft connector's rear.

Edit, UPDATE:  tried to tighten the bolts on the shaft with no luck, returned to store to get replacement, now this one has a whole new set of issues.  Either my mixture isn't right (doubt it, the previous 128LD was running off the same mixture), or there is an air intake issue.

 tank half empty,  stored horizontally, fuel drips out.  Releaved possible pressire at the cap to no acail.  concerned on fire danger and gas smell in garage.

First...I thought I had my mind made up that I wanted a 324LDX four stroke but I talked to both of my local husky dealers and both told me directly they are trash and said if I buy it they wont service it. So I hate to buy something and have no servicing dealer. The bad part is all the reviews on husky are awesome for that model.

Now let me tell you what I need/have. I have a troy bilt split boom on its last leg and want to upgrade to a husky. I have every expand it attachment known to man from edger, blower, tiller, pole saw and would like to use them still with my new purchase. I manage my 1 acre lot and I manage my 30 acre hunting property twice a year trimming limbs with the pole saw. I was in lowes and saw some huskys and looked on the expand it attachments and it listed husky as a brand that will work with them.

Now the issue. Based on talking to two dealerships I told them I wanted to buy a two stoke since they wont sell me a four stroke and told them I wanted to use my already owned attachments and one guys responce was that the only way I could use my attachments was to buy a crappier "I quote" box store version of the husky. He told me what I really needed was the 128DJX and he would sell me new attachments specfic to that model. It really sounded like he was wanting to line his pockets.

Please tell me what to buy so I get a good unit that will suit my needs. I do not need a blade attachment.