VAX ODT console fault

Folks; I have a BA23 VAX of unknown provenance, which tonight I moved from the project backlog to the workbench. It comes up and passes selftest. But any key I press on the console terminal is repeated a couple dozen times (to the limit of the input line length?). This makes it impossible to interact with ODT. Is this a normal sort of well-understood failure mode? In this session excerpt, the only thing I am sending is <BREAK> (giving me the normal chevron prompt), <ENTER> (giving me the repeated chevrons, sometimes with other characters in the pattern), ?, and h. I did not type any colons at the [XQA0] prompt, though I did try to backspace them. The behavior is the same if I remove all boards besides the KA655-B and 16 MB memory board. KA655-B V5.3, VMB 2.7 Performing normal system tests. 40..39..38..37..36..35..34..33..32..31..30..29..28..27..26..25.. 24..23..22..21..20..19..18..17..16..15..14..13..12..11..10..09.. 08..07..06..05..04..03.. Tests completed. Loading system software. No default boot device has been specified. Available devices. -DUA0 (RA81) -DUA1 (RA81) -XQA0 (08-00-2B-19-A2-D7) -XQB0 (08-00-2B-0D-83-C0) Device? [XQA0]: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : \ \\ ?26 VAL TOO LRG Device? [XQA0]: (BOOT/R5:0 XQA0) 2.. -XQA0 ?4B CTRLERR, XQA0 ?06 HLT INST PC = 00000C1A Failure. ?22 ILL CMD ?22 ILL CMD ?22 ILL CMD ?22 ILL CMD ?22 ILL CMD ?22 ILL CMD ?22 ILL CMD ok bear. -- until further notice