ORIGINAL: guver
The runtime and voltage may be irrelevent. If the packs aren't discharged then the trouble is in the truck. We would need some details to diag the vehicle.
I ran the batteries in my crawler Emaxx 3906, they ran fine for about 10 minutes then started acting this way. I put them in another emaxx 3906 with a single Titan 775 and they immediately did the same thing. I just now plugged them into my brushless Emaxx 3905 with telemetry and it was telling me that the batteries had very extreme voltage drop. Anything else you may need to know let me know.