instinct says flow control. an irix console getty uses ttyd1; i'm not
sure what netbsd does (mine's down, or i'd check). you might try
hardwiring RTS/CTS (pins 6/2) together on the din8, or doing something
similar with DTR/DCD (pins 1/7). depending on the comm program, it's
possible that it's decided the indy is dead; see if the comm program
can be configured to ignore all hardware handshaking.

some reference material:

     The DB-9 male serial port connectors on O2,
     OCTANE, Onyx2, Origin2000/200 and Origin3000/300 systems have the
     following IBM(R) PC/AT(tm)-like pin assignments:

                                -------------------
                                \  1  2  3  4  5  /
                                 \   6  7  8  9  /
                                  ---------------

                         Pin | Name | Description
                         ____|______|____________________
                          1  | DCD  | Data Carrier Detect
                          2  | RD   | Receive Data
                          3  | TD   | Transmit Data
                          4  | DTR  | Data Terminal Ready
                          5  | GND  | Signal Ground
                          6  | -    | reserved
                          7  | RTS  | Request To Send
                          8  | CTS  | Clear To Send
                          9  | -    | reserved

     The DIN-8 serial port connectors on the Indigo, Indy, Indigo2, Challenge
     S, Challenge M, Power Challenge M, and the MENET 4-Enet, 6-serial board
     (XT-FE-4TX-6A) have the following pin assignments.

                                     ---------
                                    / 8  7  6 \
                                   (  5  4  3  )
                                    \  2   1  /
                                     ---------

                      4D Compatible Pin Assignments (RS-232)
                     _________________________________________
                     _Pin___|_Name____|_Description___________
                       1    | DTR     | Data Terminal Ready
                       2    | CTS     | Clear To Send
                       3    | TD      | Transmit Data
                       4    | SG      | Signal Ground
                       5    | RD      | Receive Data
                       6    | RTS     | Request To Send
                       7    | DCD     | Data Carrier Detect
                       8    | SG      | Signal Ground

on a possibly related note, i found an assortment of GIO32 cards that
haven't been mentioned here. the snapshots are probably too old to have
the new gio bus probing stuff, can someone point me at a kernel or should
i make my own -current?