My Casio watch normally syncs six times a day from the DCF77 transmitter in Frankfurt. In freak weather it may occasionally skip a sync or two, but otherwise it has been rock steady through more than two years of operation. Until about five days ago. Every attempt has failed since then.

Meanwhile, two wallclocks have been sitting with flashing sync-icon for a couple of days, but now seem to be online again. Presumably, they have much larger antennae than my Casio.

Someone knowledgeable, please explain to me: Is the signal potentially being tinkered with, or is this just a strange coincidence?