To verify everything, I swapped back in a regular tape, no problem. I put the cleaning tape back in and the problem returns.
Checking coredumpctl (this is a Fedora system, so systemd is handling the cores) I see that... perl itself is segfaulting. Looking at the backtrace (which is automatically generated) I see that it seems to be failing down in libamanda or in the regexec function in the C library. In any case, it does appear to be related to seeing a tape that doesn't match labelstr. Please let me know if there's anything else I can try. I'm capable of testing patches, and though I'm terrible at C I can try to fix things given suggestions. Message: Process 8421 (amcheck-device) of user 33 dumped core. Stack trace of thread 8421: #0 0x00007fca19a87f86 strlen (libc.so.6) #1 0x00007fca19ae3a47 regexec@@GLIBC_2.3.4 (libc.so.6) #2 0x00007fca18f3f0d8 try_match (libamanda-3.4.5.so) #3 0x00007fca18f3f8ef do_match (libamanda-3.4.5.so) #4 0x00007fca18f40706 match_labelstr (libamanda-3.4.5.so) #5 0x00007fca12d37ef7 _wrap_match_labelstr (libUtil.so) #6 0x00007fca1ae33c50 Perl_pp_entersub (libperl.so.5.24) #7 0x00007fca1ae2c116 Perl_runops_standard (libperl.so.5.24) #8 0x00007fca1adac1ce Perl_call_sv (libperl.so.5.24) #9 0x00007fca119e71ef amglue_source_callback_simple (libMainLoop.so) #10 0x00007fca183d789d g_timeout_dispatch (libglib-2.0.so.0) #11 0x00007fca183d6e52 g_main_context_dispatch (libglib-2.0.so.0) #12 0x00007fca183d71d0 g_main_context_iterate.isra.24 (libglib-2.0.so.0) #13 0x00007fca183d727c g_main_context_iteration (libglib-2.0.so.0) #14 0x00007fca18f394d1 event_loop_wait (libamanda-3.4.5.so) #15 0x00007fca119e7c13 _wrap_run_c (libMainLoop.so) #16 0x00007fca1ae33c50 Perl_pp_entersub (libperl.so.5.24) #17 0x00007fca1ae2c116 Perl_runops_standard (libperl.so.5.24) #18 0x00007fca1adb3e56 perl_run (libperl.so.5.24) #19 0x0000000000400ce9 main (perl) #20 0x00007fca19a1b401 __libc_start_main (libc.so.6) #21 0x0000000000400d2a _start (perl) Stack trace of thread 8423: #0 0x00007fca19af6ecd poll (libc.so.6) #1 0x00007fca183d7166 g_main_context_iterate.isra.24 (libglib-2.0.so.0) #2 0x00007fca183d727c g_main_context_iteration (libglib-2.0.so.0) #3 0x00007fca183d72c1 glib_worker_main (libglib-2.0.so.0) #4 0x00007fca183feb93 g_thread_proxy (libglib-2.0.so.0) #5 0x00007fca1ab4273a start_thread (libpthread.so.0) #6 0x00007fca19b02e0f __clone (libc.so.6)