Numerous public cloud infrastructure providers today allow for access to Noisy Intermediate-Scale Quantum (NISQ) computers. Changes in the environment or the machine configuration may affect their dependability. Through analysis of real quantum computer calibration data, this work demonstrates that quantum computers available from IBM Quantum experience periods of fluctuation or abrupt qubit frequency changes. This work further analyzes the correlation between the frequency change events, decoherence times, gate errors, and machine maintenance or offline periods. The results highlight that the properties of NISQ computers change over time, affecting their dependability, but not all of the changes can be explained with publicly available data.