Puzzling HD - HDR network connection problem

I'm sure this issue come up before but I couldn't find any previous posts that matched and would appreciate any help.

I have two HDR-T2's connected to my network through DLINK DHP-206AV homeplugs. Playing through these homeplugs and then via wifi to a remote LG smart TV, I can watch HD recordings with no problem at all so I don't suspect the homeplugs are the cause of the problem. However, an HD-T2 (connected via a Solwise PL-200AV homeplug) will play HD video perfectly from the remote HDR-T2s for approximately 10 minutes but then the connection drops and the HDR-T2s disappear from the list of available DLNA devices. My ReadyNAS RN104 will still be visible in the DLNA device list and .TS files on it will play uninterrupted from start to finish, even after the HDR-T2s have dropped off the device list. I have to reboot the HD-T2 in order for it to see the HDR-T2s again. The router is a Bipac Billion 7800N and is connected to a Solwise PL-200AV homeplug.

Does anyone have any clues why this is happening? The network seems to be working ok, otherwise the ReadyNAS wouldn't remain visible. Why should the connection from the HD-T2 to the just the HDR-T2s drop?

The HD-T2 is on custom firmware 1.02.31_mod_3.00.
The HDR-T2 are on custom firmware1.03.12_mod_3.00

Thanks, BlackCat3000
I took the router out of the equation by disconnecting the network cable between it and the homeplug that connects the homeplug network to the rest of the LAN and to the internet. Bingo! I've watched 75 minutes of "Spider House" without any problem at all, with the Humax PVRs still using the same homeplugs as before.

Perhaps this is being caused by something being broadcast from a device on the LAN to the homeplug network, that the the HD-T2 doesn't like?
Have you checked if there are software updates for the various Homeplugs? I don't know about DLINK Homeplug adapters but some TP-Link Homeplug adapters have a bug with DLNA that causes similar problems to yours and is fixable by upgrading the software.
Hi. Yes, thankyou, I saw the post about the TP-Link firmware update and I read that it mentioned the problem was resolvable by either installing the firmware update or by enabling IGMP on the router (it's already enabled). The Solwise homeplugs are not new by any means and came with the most recent firmware already installed. TheDLINK homeplugs were supplied by TalkTalk last year and I can't find updated firmware for my specific model (DHP-206), only for theDHP-106 model, which I'm wary of trying. Ironically, I do have some very new TP-Link homeplugs as well, and the problem occurs with any and all of them if they are connected to the LAN via the router.

I have a workround now, so I'm happy, but Im still interested to find the cause of all this.