Do you want the false immediately if a close happens or do you want that also only after the 3 seconds are over and its closed?
Edit:
Than you could try this:
[{"id":"5c34e9c0.c762","type":"inject","z":"c38d0f4.885dff","name":"Open","props":[{"p":"payload.ContactSensorState","v":"1","vt":"num"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":190,"y":360,"wires":[["e92a0fda.792e7"]]},{"id":"c1c9de36.978c98","type":"inject","z":"c38d0f4.885dff","name":"Closed","props":[{"p":"payload.ContactSensorState","v":"0","vt":"num"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":190,"y":440,"wires":[["e92a0fda.792e7"]]},{"id":"e92a0fda.792e7","type":"change","z":"c38d0f4.885dff","name":"Save current","rules":[{"t":"set","p":"Contact1","pt":"flow","to":"payload.ContactSensorState","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":350,"y":400,"wires":[["5cb8240e.ebe41c"]]},{"id":"5cb8240e.ebe41c","type":"switch","z":"c38d0f4.885dff","name":"Open?","property":"payload.ContactSensorState","propertyType":"msg","rules":[{"t":"eq","v":"1","vt":"num"}],"checkall":"true","repair":false,"outputs":1,"x":510,"y":400,"wires":[["36c9d380.37e40c"]]},{"id":"36c9d380.37e40c","type":"trigger","z":"c38d0f4.885dff","name":"","op1":"","op2":"","op1type":"nul","op2type":"payl","duration":"3","extend":false,"overrideDelay":false,"units":"s","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":660,"y":400,"wires":[["50ae92ea.20e8ac"]]},{"id":"50ae92ea.20e8ac","type":"change","z":"c38d0f4.885dff","name":"Open or Close?","rules":[{"t":"move","p":"payload","pt":"msg","to":"original","tot":"msg"},{"t":"set","p":"payload.on","pt":"msg","to":"($flowContext(\"Contact1\") = 1)? true : false","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":840,"y":400,"wires":[["35542b79.1784b4"]]},{"id":"35542b79.1784b4","type":"debug","z":"c38d0f4.885dff","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":1030,"y":400,"wires":[]}]