How did I kill my servo?

I had a single Hitec HS-7955TG in my Traxxas E-revo & it died.I was running it my E-Revo(5605) Smc 9000 2s 28C lipo batteries with a CC Monster Mamba 2220 combo & they day before I noticed that that steering & forward speed would cut out(stop),then a second later everything went back to normal.The next run was fine & I their wasn`t any sign of the same probelm,but I noticed the bottom of the servo had melted(two little bubbles right above a eletonic component) & the servo was hot.Well the next run the servo died.
I`m thing it was user error(me) but I put two stock E-revo servos back in & their hasn`t been a problem since.

heres what my E-revo(5605) setup
-CC Mamba Monster 2200 combo
-SMC 9000mah 28c 2s lipo
-18 tooth pinion & 65 tooth spur
-Proline badlands on Rpm rims
-proline single servo arm
-Traxxas Heavy Duty Servo Saver Spring
-single Hitec Hs-7955TG servo
-Futaba 3PM FM radio & receiver(older crystal type radio)