I narrowed this down to a problem with my hw key. When running pcscd in debug mode, the following repeats over and over when tellicast is running.
00000029  winscard_svc.c:361:ContextThread() Received command: CMD_STOP_WAITING_READER_STATE_CHANGE from client 8
00000008  winscard_svc.c:440:ContextThread() CMD_STOP_WAITING_READER_STATE_CHANGE rv=0x0 for client 8
00000028  winscard_svc.c:361:ContextThread() Received command: CMD_WAIT_READER_STATE_CHANGE from client 8
00000006  winscard_svc.c:832:MSGSendReaderStates() Send reader states: 8
I don't remember this happening with the old client/driver combo. I tried a different distro on a different computer and the result is exactly the same. Without the key plugged in, tellicast is running normally, but it's not much of a solution. I'm clueless at the moment, really.
I can't believe Eumetsat hasn't noticed this, or maybe they're just running some ancient version of Linux? I'm running Ubuntu Server 18.04.2 LTS and Fedora 30.