Update: I've noticed the warranty on my PC was still valid so I contacted Dell support (Italy) and in less than a week my PC has been fixed. They didn't give me the specifics, but I think the problem was definitely hardware. Hope you all will find a solution, too! 
I have been having some problems with my keyboard on my Dell G5 5587 laptop. A column of keys have stopped working: 2,w,s,x. Recently I replaced the thermal paste on the CPU and GPU (nightmare). In the process I had to unplug all the ribbon cables and then plug them back in later. I have since used canned air to clean the ribbon cable and the connector and I have re-seated the cable at least three times to to no avail. However the keys aren't completely dead. I have noticed that sometimes If I hold down one of the non-functional keys and press the key to the right of it (for example hold down s and press d) it will work. Also if I do this enough and tap the non-functional keys enough they can temporarily start working again, however they sometimes stop working again and they always seem to stop working after I restart or go into and back out of sleep mode. I have also tried reinstalling drivers twice and it doesn't do anything. A new keyboard isn't that much but replacing it is a huge pain in the *** for this laptop. Because of me working on the laptop recently and since it is a whole column, part of me thinks it is a hardware problem, but since it didn't happen for a few weeks afterwards and came on slowly and because of them working sometimes part of me thinks it is a software problem. Anyone else had this problem before? Any advise? Also how much would it cost to send it to dell to be fixed of of warranty?
G5 5587 Keyboard Problems