Yeah, this one's common. You're probably wearing down the coupler by starting on a high speed with chunky frozen items.
Don't just crank it to high. Use the pulse button first to break up the chunks. Turn and hold the control dial from (O) to (P) for short bursts. This lets the fruit fall to the blades. Once it's broken up, then you can progress to a higher speed for a smoother blend.
If that didn't work, check the coupler teeth on the base under the jar. Pushing down on the lid or removing the jar while it's spinning can cause them to come off. Always let it stop completely.
Heads up: Starting low and pulsing first actually gets you a smoother smoothie faster. High speed initially makes stuff float in the middle and takes longer.