Letting anyone seal over old silicone
New silicone does not bond to old silicone, and mould trapped underneath grows straight through the fresh bead. If the technician is not spending most of the job on removal and drying, the reseal will fail within months. Ask to see the joint clean and dry before the new bead goes in.
Putting a full-motion TV arm into bare plasterboard
An articulating arm multiplies the TV's weight into leverage at a few fixing points, and plastic plugs in gypsum cannot resist it. The mount holds during the demo and fails weeks later. Insist on metal studs, a backing board, or a different wall.
Skipping the building permit and losing the slot
In permit-controlled towers, a technician stopped at security is a wasted visit that you may still be charged for. Five minutes with building management before booking, asking about NOCs, service-lift rules and drilling hours, protects both your slot and your deposit with the building.