https://gitlab.synchro.net/main/sbbs/-/issues/1120#note_8790
Ok, it looks like data_transfer_end() is trying to print something on the terminal channel that doesn't exist.
```
Thread 32 (LWP 437476 of process 13533 "sbbs/termInput"):
#0 0x00000009031ce4da in Terminal::inc_column (this=0x3ee01631ef00, count=1) at terminal.cpp:206
#1 0x00000009031ce5a1 in Terminal::dec_column (this=0x3ee01631ef00, count=1) at terminal.cpp:234
#2 0x000000090301eeee in sbbs_t::set_authresponse (this=0x3ee01631ef00, activate_ssh=67) at answer.cpp:36
--Type <RET> for more, q to quit, c to continue without paging--
#3 0x0000000903046a39 in sbbs_t::petscii_to_ansibbs (this=0x3ee0937e8b00, ch=0 '\000') at con_out.cpp:279
#4 0x0000000903047cc0 in sbbs_t::term_rows (this=0x3ee0937f7c74, user=0x3ee0937e8b00, str=0x4343000000 <error: Cannot access memory at address 0x4343000000>, size=69134268202100) at con_out.cpp:583
#5 0x00000009030474ca in sbbs_t::cp437_out (this=0x3ee0937e8b00, str=0x430000090301dbea <error: Cannot access memory at address 0x430000090301dbea>, len=69134268140288) at con_out.cpp:368
#6 0x0000000903045e34 in sbbs_t::ctrl_a (this=0x3edffeb1c008, x=0 '\000') at con_out.cpp:938
#7 0x00000009030477fb in sbbs_t::cp437_out (this=0x3ee0937e8b00, ich=16095) at con_out.cpp:457
#8 0x000000090304c657 in sbbs_t::data_transfer_end (this=0x3ee0937e8b00, local_binary_tx=0 '\000', remote_binary_tx=0 '\000') at download.cpp:116
#9 0x00000009031bc7a8 in parse_dir_handle (sbbs=0x3ee003860820, handle=0x90315c501 <input_thread(void*)+49>) at sftp.cpp:818
#10 0x00000009031b8a5f in sftp_write (handle=0x3ee003820028, offset=0, data=0x80003523de30, cb_data=0x3ee0937e8b00) at sftp.cpp:1573
#11 0x00000009036dedc9 in s_read (state=0x3ee003901000) at sftp_server.c:129 #12 0x00000009036de3bd in sftps_recv (state=0x3ee003901000, buf=0x93523f010 "", sz=26) at sftp_server.c:421
#13 0x000000090315d9bd in crypt_pop_channel_data (sbbs=0x3ee0937e8b00, inbuf=0x93523f010 "", want=4000, got=0x93523e064) at main.cpp:2052
#14 0x000000090315cce7 in input_thread (arg=0x3ee0937e8b00) at main.cpp:2279 #15 0x0000000908925b52 in ?? () from /lib/libthr.so.3
#16 0x0000000000000000 in ?? ()
Backtrace stopped: Cannot access memory at address 0x935240000
```
Digging in deeper.
--- SBBSecho 3.37-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)