WD40 is more a cleaning agent than a lubricator. Use lubricating oil to keep the lock working smoothly.
I have the same problem periodically. Spraying lock oil in there solves the problem for a long time. I guess it does not have to be specific lock oil, but they have a convenient straw to get the oil inside the lock barrel.
http://www.wd40.co.uk/faq.html
"What does WD-40 do?
WD-40 fulfils five basic functions: 1. CLEANS: WD-40 gets under dirt, grime and grease to clean. It also dissolves adhesives, allowing easy removal of labels, tape and excess bonding material. 2. DISPLACES MOISTURE: Because WD-40 displaces moisture, it quickly dries out electrical systems to eliminate moisture-induced short circuits. 3. PENETRATES: WD-40 loosens rust-to-metal bonds and frees stuck, frozen or rusted metal parts. 4. LUBRICATES: WD-40's lubricating ingredients are widely dispersed and tenaciously held to all moving parts. 5. PROTECTS: WD-40 protects metal surfaces with corrosion-resistant ingredients to shield against moisture and other corrosive elements."
I have the same problem periodically. Spraying lock oil in there solves the problem for a long time. I guess it does not have to be specific lock oil, but they have a convenient straw to get the oil inside the lock barrel.
http://www.wd40.co.uk/faq.html
"What does WD-40 do?
WD-40 fulfils five basic functions: 1. CLEANS: WD-40 gets under dirt, grime and grease to clean. It also dissolves adhesives, allowing easy removal of labels, tape and excess bonding material. 2. DISPLACES MOISTURE: Because WD-40 displaces moisture, it quickly dries out electrical systems to eliminate moisture-induced short circuits. 3. PENETRATES: WD-40 loosens rust-to-metal bonds and frees stuck, frozen or rusted metal parts. 4. LUBRICATES: WD-40's lubricating ingredients are widely dispersed and tenaciously held to all moving parts. 5. PROTECTS: WD-40 protects metal surfaces with corrosion-resistant ingredients to shield against moisture and other corrosive elements."