An extra energy shift between emitted and received radiation on a rotating disc - next to the conventionally recognised second-order Doppler shift - has been revealed in a series of recent Mossbauer experiments, where a radioactive source is fixed at the centre and an absorber is attached to the rim of the rotating disc. This disclosure gives indication to a possible violation of the "clock hypothesis" by Einstein: i.e. the independence of the rate of a clock on its acceleration. At the moment, there seem to be two plausible interpretations of this result: (i) the deviation of the geometry of the rotating disc from that predicted by the general theory of relativity (GTR), or (ii) the existence of a specific maximal acceleration in nature, when transformation between two accelerated frames differs from the corresponding transformation of the relativity theory. We take a closer look at both ways leading to the violation of the clock hypothesis; particularly, by analysing the outcomes of recent experiments in rotating systems and by suggesting a new Mossbauer rotor experiment to determine the most feasible mechanism for testing the dependence of the rate of a clock on its acceleration.