I recently replaced the upper and lower plastic rotor heads with aluminum ones (the plastic ones broke due to a few hard landings). I was re-trimming the heli, adjusting the pushrod lengths, when I noticed I wasn't getting anywhere. One moment lengthening, the next shortening. Then I realized the swashplate assembly had seperated. I snapped it together and tried again, but it came apart again. I replaced it with a new plastic assembly. I started the trimming procedure again, short liftoff, hover a few seconds to note the direction of drift, then landing. After a few of these I noticed the new swashplate had seperated just like the old one. I assumed the first one failed as a result of one of the hard landings. But there was no reason the new one should have failed. The only thing I can figure is this is a result of switching to the aluminum rotor heads. Does anyone have any idea why this is happening?