Engine experiencing problems during startup and shutdown

Hello guys,

I own a Vento 1.6 tdi 2014. Recently what happened was that i try to start my car with the spare key that cones extra with car and suddenly the glow plug icon started flashing and than after starting up car turned off immediately in like 2 secs. Than it just wouldnt start until i re insert thr key. And it will repeat the same process again. Note: the remote on my spare key doesnt work.

Than i tried starting the car with the old key that i had been using all this while and it turned on normally. And glow plug icon too stopped flashing.

However since some time i noticed that now whenever i start my car it kinda seems hard for it. It like coughs two times instead of one. And i did get my battery and glow plugs and injectors checked and they are all okay.

Can somebody tell me whats going on with my car. Is it just the age or i am going to encounter some serious issue in future.

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