I suspect the serial write error is related to the WF command I noticed in my original logs. Perhaps this debugging information will be useful?
(gdb) break /home/stellarmate/Projects/indi/drivers/filter_wheel/pegasus_indigo.cpp:140 Breakpoint 2 at 0x558bec9db0: file /home/stellarmate/Projects/indi/drivers/filter_wheel/pegasus_indigo.cpp, line 140. (gdb) c Continuing. Breakpoint 2, PegasusINDIGO::TimerHit (this=0x55b18152b0) at /home/stellarmate/Projects/indi/drivers/filter_wheel/pegasus_indigo.cpp:140 140 if (sscanf(response, "WF:%d", &position) == 1) (gdb) p response $4 = '\000' <repeats 127 times> (gdb) p position $5 = -1