SamyGO

I just upgraded from Samsung UE40HU6900 to UE40JU7000 model (this is European ver. of JU7100).
Most of the time we play recorded cartoons for our toddlers.
While HU6900 played *ts. *.mts, *.mkv, *.mp4 files from small home DLNA server (Western Digital 900 Central router) almost instantly (2-3 seconds), JU7000 needs 1-2 minutes (!!) to open a file, if opens at all, as it happens there is a black screen only.
I do not see the above JU7000 problem with files played by Twonky Media service from another file server (QNAP).
Also building files thumbnails takes ages for JU7000 when compared with older HU6900.
Wired (ethernet) LAN.
Is there any problem with JU7000 and DLNA service? Buffering? Any suggestions (as to change settings in service menu)?

Again, question for H series / J series users regarding reading media files (movies - mts, mkv, ts, avi, mp4, mov) through DLNA over LAN ('pulling' files, with no software player/file server i.e. Twonky Media etc.):
I notice significant difference (seconds vs. minutes) of reading time by my former HU6900 and my today's JU7000 TVs, while HU6900 read (buffered) media files from Western Digital MyNet 900 Central router / DLNA file server within seconds, JU7000 needs minutes (!!) or even refuses playing them.
It looks as if JU7000 needed much more buffering, to the extent it's not acceptable.
There is wired gigabyte LAN ethernet (nevertheless Samsung Smart TVs have only 100 Mbps RJ45 interface).
What is strange, there is no significant reading time difference between these HU and JU TVs when reading files from my second router / DLNA file server Netgear WNDR4720 Centria.
What Samsung 'improved" from its 2014 Smart OS to the 2015 Tizen that so worsened reading DLNA files over LAN?