Top loader washing machine inner drain hose coming loose during cycle

Besides the obvious check of the mechanical connection (did a plastic barb that should be helping hold this hose in place break off?), I'd be concerned about a clog or obstruction in the (external) drain hose itself.

If the drain hose is kinked or obstructed, the pressure generated by the drain pump could be enough to pop the internal hose off its fitting.

My next guess would be that the internal hose has gotten stiff with age, and is more prone to getting yanked off its connector when the drum moves around. Final culprit could be an issue with the washer's suspension, allowing the drum to move much more than it's supposed to (beyond the hose's limits).