Weird led

[jjjjjjjjjjjj]

About two weaks ago I sent my Xperia X to service, becouse the motherboard was dead. Today I finally recived my phone back. Everything is working great but one thing is really unusual. When I click power button or volume up button, led blinks in red color. This is happening even when my phone is turned off. (My phone was full charged). Moreover I have launched software fix in pc compation and that bug is still there. The led is on as long as I hold or click on this buttons. Is that a special debug mode that sony service has forgot to turn off when they send the device back to me? Is it possible to fix that bug without sending xperia back again to service ? 

PS: Sorry for my bad English, it's not my native language.

[Andy_g2]

If I understand you correctly you have repaired the phone using pc companion

Have you tried to use the phone in safe mode? Click here to see how to place phone in safe mode.

It might not help but its best to check, just in case.

Do you have an SD card inserted and have you tried without?

[jjjjjjjjjjjj]

Yes yes and yes. I think that this issue is not connected with rom of my device, but with kernel or maybe this replaced motherboard is not so good (this idea came to me becouse of that when phone is turned off the led turns on when I click the power button or volume up). I though thats maybe a secret debug feature for people that work in sony service and that maybe it can be turned off.