I notice this too, that DVBLink Player/viewer always has problems the first 10-15 seconds when starting some FHD (1920x1080) IPTV streams....
DVBLink Player/Viewer buffers or shows artifacts, while VLC plays the same stream flawlessly straight away without buffering or artifacts

So this is definitely a issue from "DVBLink for IPTV" and not from Kodi, because also when starting the same IPTV stream directly from a local m3u in Kodi, instead of the IPTV source, the stream also plays flawlessly straight away

DVBLink server 6.0.0 build14499, DVBLink TVSource 6.0.0 build14061, DVBLink for IPTV build 13107
Kodi 18.0-ALPHA1 Git:20180125-7379a75, Win10 Pro x64 1709 build16299.125