rx_stream for 8 bit samples not working all the times when uisng c++

Issue Description

I'm creating a monitoring tool for radios and when I try to do some recordings using the sc8 format sometimes I just receive 0s, after I do a recording using sc16 the sometimes the sc8 works fine.

Setup Details

I'm using the binary installation of the UHD 4.5.0.0-release and happened to me too with the 4.3-pre-release. I've tried it on a B205 mini-i and a X300, in both happens the same problem. sc16 works fine, fc32 and fc64 too, but when I use OTW sc8 and CPU format sc8 doesn't work reliably.

Expected Behavior

When you configure the rx_streamer to use sc8 I expect to receive sc8 samples.

Actual Behavior

Receive full array of 0s.

Steps to reproduce the problem

Using the rx_to_file.exe example you can recreate this behavior. Just use big sample rates and you can see that some of the recordings you do are just full of 0s.

EttusResearch / uhd