Re: carb ????
It is possible the float valve was being held open by trash and it finally flowed through. The float level can change due to hard bumps but that is rare, very rare. If the float is too high it might not allow full shut off of the needle valve but that too is not common.
These little 2 stroke engines are temperamental and can be effected by temperature, humidity and many other factors that might explain the difference in running conditions you described. You didn't say how much run time is on this engine but they tend to get better with age, like wine, and run stronger and more consistent the more miles they have on them.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"