acnode is stuck in open (green) mode even if the card has been removed

[mentarus]

acnode is stuck in open (green) mode even if the card has been removed, the server sees something like this (real example from the lasercutter):

| * | * | 2016-08-13 13:53:21 | Access Started |
| * | * | 2016-08-13 10:20:42 | Time Used |
| * | * | 2016-08-13 10:09:57 | Time Used |
| * | * | 2016-08-13 09:57:28 | Time Used |
| * | * | 2016-08-13 09:42:18 | Access Started |

This should never happen as there should always be an Access Finished message after a card is removed.
It's quite an major bug and I have suspicions that people are exploiting use the tools without being logged