I am seeing the same results using the zlib plugin.
Nov 30 16:04:34 iceberg dovecot: imap(eric): Panic: file istream-zlib.c:
line 416 (i_stream_zlib_seek): assertion failed: (ret == -1)
Nov 30 16:04:34 iceberg dovecot: imap(eric): Error: Raw backtrace:
/usr/lib/dovecot/libdovecot.so.0(+0x95272) [0x7f30f0fa2272] ->
/usr/lib/dovecot/libdovecot.so.0(+0x9536d) [0x7f30f0fa236d] ->
/usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f30f0f38951] ->
/usr/lib/dovecot/modules/lib20_zlib_plugin.so(+0x5883) [0x7f30f0763883]
-> /usr/lib/dovecot/libdovecot.so.0(i_stream_seek_mark+0x1e)
[0x7f30f0fad47e] ->
/usr/lib/dovecot/libdovecot-storage.so.0(istream_raw_mbox_seek+0x108)
[0x7f30f12a2078] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mbox_file_seek+0x47)
[0x7f30f12a2867] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x7e4ec)
[0x7f30f12ac4ec] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x81317)
[0x7f30f12af317] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mbox_sync+0x48)
[0x7f30f12af8b8] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mbox_storage_sync_init+0x85)
[0x7f30f12afa45] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mailbox_sync_init+0x3b)
[0x7f30f126f02b] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mailbox_sync+0x37)
[0x7f30f126f177] ->
/usr/lib/dovecot/libdovecot-storage.so.0(index_storage_get_status+0x31)
[0x7f30f12e60c1] ->
/usr/lib/dovecot/libdovecot-storage.so.0(mailbox_get_status+0x31)
[0x7f30f1270bc1] -> dovecot/imap(imap_status_get+0x77) [0x55db687c72f7]
-> dovecot/imap(cmd_status+0x18e) [0x55db687b9cce] ->
dovecot/imap(command_exec+0xa5) [0x55db687bf735] ->
dovecot/imap(+0x199c2) [0x55db687bd9c2] -> dovecot/imap(+0x19a4c)
[0x55db687bda4c] -> dovecot/imap(client_handle_input+0x1b5)
[0x55db687bde55] -> dovecot/imap(client_input+0x86) [0x55db687be3c6] ->
/usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x52) [0x7f30f0fb6dd2]
-> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x109)
[0x7f30f0fb8409] ->
/usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0x3c)
[0x7f30f0fb6e6c] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x38)
[0x7f30f0fb7018] ->
/usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13)
[0x7f30f0f3ee93] -> dovecot/imap(main+0x328) [0x55db687b0e68]
Nov 30 16:04:34 iceberg dovecot: imap(eric): Fatal: master:
service(imap): child 3956 killed with signal 6 (core dumps disabled)
