Pipelines operating in deep and ultra-deep water environments are subject to high external pressures. These extreme conditions can trigger structural instability and potential failure which pose significant environmental, economic, and safety risks, making the integrity and safety of subsea infrastructure a major concern. The collapse pressure of a pipeline results from a complex interplay of factors, including geometric considerations, material properties, temperature, loading conditions, installation procedures, and manufacturing processes. This complexity makes it quite challenging to develop a mathematical model that accurately captures all of these aspects. In this context, pipe testing plays a crucial role in providing valuable insight and validating theoretical models. The present work specifically focuses on the collapse ring testing patented by VerdErg Pipe Technology in order to account for the results from some recent additional tests. These results are here mathematically interpreted other then with reference to the influence of the out-of-roundness, also with respect to the elasto-plastic buckling of a ring on an elastic foundation, taking into account both plastic deformations and the radial restraint provided by the friction between the seals and plates of the testing apparatus. The work shows that some test conditions, and in particular the actual lubrication of the gaskets, can also unexpectedly influence the value of the measured collapse pressure.