Enable RTP latching | SFB Trunk Configuration

Hello Community , 

I have a SFB 2015 deployment where we were consistently saw audio lags of 15 seconds for incoming PSTN calls when "Enable RTP Latching" was not enabled on the trunk configuration. 

Audio codes SBC's did not suffer from this problem but Ribbon SBC's did. So we had to set up a trunk specific config for Ribbon with this option enabled. 

Does anyone know exactly what "Enable RTP latching" is doing ? Documentation is sketchy at best and i cant glean anything from my log captures. 

Thanks for your help