Why is person hearing loud echo? Motorola One Zoom XT2010.

Hello , I am experiencing some issues with Motorola One Zoom (XT2010). I was changing LCD - everything was alright, I manage to do it after I watched video tutorials how to change LCD on that type of phone - LCD is changing from the top (you just dismantle LCD), not through the back cover like most of the smartphones so its no need to do complex dismantle of components in the phone (flex, battery, etc.). So I am pretty sure there is no way that I damaged it in some way. My problem is that after this changing of LCD guy, which phone it is, called me that when he is calling with someone (everyone he is calling with) he is experiencing that person on the other side of phone call is hearing really loud echo of himself. Has someone experienced something like this? Has it something to do with changing of the LCD? Thanks for every tip and answers.