unable to recover simple passwords

[dipstick]

Started messing with this again and tested my uncracked Tripcode (16000) hashes with john. It cracked over 1000 very simple hashes instantly. 
For example, hashcat was not able to recover:
1
a
AA
00
%
'
''
'E
Seemingly has a problem with 1-2 characters. Although, some of the recovered passwords are that length.
Implementation issue?

Previously, I only noticed "special" characters not being cracked:
https://hashcat.net/forum/thread-11343.html

Any idea why hashcat can't recover them?