LG Electronics — Problem in Mobile Phone after Service

Had taken my LG G8X to Bangalore service center when the phone had touch issue on the screen. Got it replace under warranty. This service was done in the month of Oct 2021. Now the back panel is getting removed as I see gap being formed between the back panel and the middle frame. The adhesion was not proper and due to this I'm suffering as my phone will no longer be water resistant. This was completely not my fault and I am having to be burdened with this. Called service center of Chennai and they say the gap will form under normal circumstances. Don't really know if they're trained to service phones after getting such a response. Called customer care as well with escalation to supervisor, yet didn't get connected to the supervisor but was put on hold for a long time.