Itemsize mismatch?

I’ve been attempting to add a UDP sink to my ATSC transmitter. The issue
seems to be the UDP sink is sending samples of 8, whist the modulation
stage is expecting a itemsize of “1” (It used to take in TS files
through a file sink).

Scouring through documentation, Google-fu, nothing has netted me much of
an answer. The output and input are both complex. Resampling doesn’t
seem to work, nor does converting the complex to anything else.

And yes, this is what I want to do.

Any suggestions?