I needed to extend a 50m cable by about 1 meter. I know that the best solution would be to make a new run but it's very difficult to swap the cable so I tried to avoid it. As RJ45 couplers would take a few days to be delivered, I bit the bullet and soldered the two cables together. While soldering also I managed to break a small part of the orange wire of one side so to extend that I used some salvaged resistor leg and when I finished the soldering wrapped everything in heatshrink tubing. It was tested afterwards and the average ping (my PC -> router) was either 1ms or <1ms with 0% packet loss.
After 2 weeks and having changed my main router (as per ISP's instructions for something unrelated) comes today. I noticed websites took much longer to load but on speedtest.net the speed was good. So I pinged 192.168.1.1 again and sure enough there was a lot of packet loss and higher delay. I wiggled the junction of the 2 cables a bit and after a couple of minutes the problem was fixed again. Now I'm again having 1ms latency but there are some spikes that go as high as 800ms.
My question: Is it the cable, the new router, something else or is it normal to have spikes after around 1800 ping packets?