I'm not quite sure why this is happening but it is rather weird and I'll try to explain the best I can, First some info.
I received a TBS5922 as a replacement for a QBOXS2 that was overheating (thanks to support for sorting that out for me!), anyway, I'm currently using the 5922 connected to a HP N40L Microserver (AMD Turion(tm) II Neo N40L) running Debian testing (Kernel 3.2.0-2-amd64) with the latest drivers (120216).
I intended to use the box with TVheadend which runs perfectly fine on the system with other tuners (DVB-T) but whenever I use the 5922 with TVheadend the 5922 gets hotter than it should and it gets worse if I actually watch something over the network via TVheadend, the picture glitches (VLC) and it takes about 10 seconds for the box to change channels, sometimes failing and blurts out "tbs5922fe - Current Delivery System and Mode are unknown" to dmesg.
I left the box alone for 10 or so hours, when I went to touch it, It was bloody hot enough to actually burn you, If you let it.

Now this is where it gets interesting. I also use DVBStreamer, The 5922 barely gets warm, takes 3 seconds at max to tune to a channel and captures freesat EPG data no problem, when I stream a service over my network I get no glitching (again using VLC) whatsoever.
Once again I left the box well alone for 7 hours or so running DVBStreamer streaming "BBC One HD" to my media center. The 5922 remained barely warm.
Isn't that odd?
Now I don't know that the difference is between the two software but there clearly is something not quite right, I suspect different tuning methods? Although I'm pretty sure most DVB software on Linux uses the same DVB API.
Could it be the driver? I just don't know, at the moment the box is only usable with DVBStreamer which means I have to manually set the service via telnet!