Vaillant EcoTec Pro not reaching set temperature

[Emre]

Hello! We have 3 years old Vaillant boiler and recently we noticed that it's not reaching set temperature. I set the temp to 50 deg C, and then when we open the water, it starts burning and burns about 4-5 sec. then it stops. around 46 deg C. Water cools down a bit, then it starts burning again. this time burns about 2-3 sec and stops. I don't think it's related to temperature but it tries to burn and something make it stop. There is no error code on the screen. I will attach a video of the problem as well. I'll be appreciated if you can give me an idea what is it about. Thank you!

video: video-1603189609 - https://streamable.com/mfr5v4

 

[Scott_D]

Have you got a magnetic filter fitted?

 

[Aquarius]

Could be an issue with the flow turbine?

 

[Scott_D]

It could be one of a few different faults.
If its been registered and serviced and fitted to a clean system it should still be under warranty