Tvheadend

Hello, I am using TvHeadend 4.0.7 on my WeTek Play with Open Elec 6.0. Watching TV works mostly good, however I encountered a strange problem: When I start up a channel it takes quite some time (8-10 sec) until I hear sound and see a picture. The picture freezes than (sound is okay) for another 3-4 seconds. After that everything works fine. However when I afterwards switch between channels, it only takes the 3-4 seconds channel-switch-time without any problems. This occurs only when I start a new channel without watching tv before.

Before I have used TvHeadend 3.9 and this problem has not existed. I don't know if this is a TvHeadend problem, or a pvr.hts/OE problem. How can I track this down? What logs can I provide?