[Freeswitch-users] What are these log entries?

Hello, Out of nowhere we have started to get a lot of these: [WARNING] switch_core_file.c:408 File has 1 channels, muxing to 2 channels will occur. [WARNING] switch_core_file.c:408 File has 1 channels, muxing to 2 channels will occur. [WARNING] switch_core_file.c:408 File has 1 channels, muxing to 2 channels will occur. I've tried to look in the code for an explanation, without succes. Does anyone know why this is appearing ? Thank you, Allan *Running: FreeSWITCH Version 1.8.7+git~20190801T142138Z~b4a4ac33f8*