1/8 buggy problem

[Hyper-5]

hey, l was just using my 1/8 hyper 8, and the power on it just keeps cutting out. When l give it a full punch sometimes it goes slow as if the battery is low, but when l lift it off the ground its fine untill its back on the ground. Does anyone know what is wrong, lm not to sure if its the motor or esc, (its not the batteries because l tried it with three differnent ones)