Poor bandwidth after re-coupling an Ethernet cable
Have you ever heard of the requirement to maintain impedances on fast data lines? 940 Mbps can be regarded as a frequency of 470 MHz in that the equivalent symbol rate is 940 Mbps and at this frequency, one wavelength is about 0.64 metres (as an air borne radio wave). In cable this reduces because the velocity of propagation is something like 70% so the wavelength becomes smaller at about 0.45 metres.

As a golden rule, to avoid disrupting impedances too much and causing bad reflections, engineers use the rule that you should avoid uncontrolled runs of data that are more than one-tenth of the wavelength. One tenth of 0.45 metres is 45 mm.

So if you have splayed open the cable in order to attach crocodile clips and the overall length of that "modification" is greater than about 45 mm (including the croc clip length) then you are on the verge of asking for trouble.