Earpiece suddenly very low volume

Hi, a month ago I replaced screen as a whole front assembly, everything went as expected, all the features of the phone worked well, nice. Now, after a month on one morning, my phone calls become suddenly very silent. The other side hears me well, but even with the maxed volume I can here them clearly only in a totally quiet room. Loudspeaker works as expected. No updates happened in a while, so it's probably not a software issue, I reopened the phone, to check the contacts, or mechanical obstacle, forgotten foam, found nothing. Everything seems to be visually OK. Now I am not entirely convinced that it is related to the screen replacement, but that's quite a big thing for all phones so there's a good chance there is a connection. Happen to anyone too? Any ideas?