The Brain not working as expected (or is it me?)

[Snoopy]

UPDATE:
new error occurs with more complicated hashsets, all runs with same settings (except --session)

same hashtarget (stats below)
Hashes: 79405 digests; 79405 unique digests, 78789 unique salts

bruteforce for testing purpose, length one with mask ?a
every run ends up with its own session-id and attack-id

Session..........: test-bf (Brain Session/Attack:0x59aa9845/0x9d7dad6d)
Session..........: hashcat (Brain Session/Attack:0x1b4ce4de/0xfff95e8d)
Session..........: hashcat (Brain Session/Attack:0xc6bf0189/0x7f416e07)
Session..........: hashcat (Brain Session/Attack:0x7240377d/0x4112219a)
Session..........: test-bf (Brain Session/Attack:0x7009c96f/0x787bc4dd)
Session..........: test-bf (Brain Session/Attack:0xff66cad7/0xf3a48091)
Session..........: test-bf (Brain Session/Attack:0x4f0fa7d0/0xff48a0d0)

the hashtarget has some malformed inputs (Token length exception) but this should not be the problem as hashcat exlude them automaticly?