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.
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.
Judging the quote instead of the method
The cheapest quote often prices a different job: silicone over silicone, plugs instead of proper anchors, no anti-tip strap on the wardrobe. When quotes differ widely, ask each vendor how they will do the job. The one who mentions wall type, anchors and cure times without prompting is usually the one worth paying.