If some clown has put a staple or nail through cable internet coax, then to remove the nail and call that a job done is incompetent, I'd have thought that they'd replace the cable if it's between the wall box and the hub?
Because of the huge range of frequencies and intensive spectrum use with cable internet & TV systems, the coax is hugely sensitive to problems of radio frequency noise ingress, and to deformation of the circular profile of the cable as this can cause internal signal reflections. The main symptoms for you would be a connection that may not be as reliable as it should, and poor latency which would give a poor experience gaming, making video calls, on Microsoft Teams and so forth.
Regarding the unpaid compensation that's a breach of applicable regulations (I presume this was CISAS, as Ombudsman Services only recently took over as adjudicator for VM), contact CISAS for advice. If need be start a new complaint with VM demanding they pay up that amount, and take that to Ombudsman Services (of if OS won't accept that, then search MoneyClaimOnline, and make a claim through the onle small claims court process, that'll be pretty straightforward with an unsatisfied adjudication.
You should also make a new complaint to VM for compensation for the circa two years of crap connection and crapper customer service. Wait for that to be fobbed off, reject any resolution letter VM send and ask for a deadlock letter, and go straight to Ombudsman Services. Don't accept any of VM's feeble £15-40 compo offers.