Yes, many times. It is likely that these keys are not gapped properly. The gap is the space between the open end of the reed and the reed plate. It should be roughly the same as the thickness of the reed. Probably the gaps need to be opened slightly. The problem with the gaps will probably be visible once you open up the melodica and are able to look at the reeds. The end of the reed can be pulled upward, very gently, with a plastic toothpick or the end of your finger — or even better by sliding a thin piece of cardboard under the reed so there’s some support and lifting that from the end, gently pulsating the reed up to slightly increase the gap. Do this gradually; if it’s opened too far, the reed won’t sound. If you search the Forums here for “gap” or “gapping,” you’ll find more detail. Do be very careful, but I have gapped hundreds of reeds and only snapped one, which I believe had already failed.
The problem was probably caused by someone blowing way too hard on the melodica, though that can also cause reeds to fail and be ruined — which is your worst case scenario. I’m interested to hear how this works out for you.