There are no known bugs in Alan 3.0beta3, there are over 1200 testcases that are run before each build is made available, so nothing much slips through.
But, if you are using an older interpreter to run a game produced with the alan3.0beta3 compiler, the interpreter might crash if the game uses attributes for the entity class. So it is actually a backwards compatibility problem rather than a bug.
Older interpreters are found in distributions of Gargoyle, the very nice and popular multi-IF-format interpreter.
You can suspect that you have encountered this issue when the interpreter stops and emit either
SYSTEM ERROR: Unknown attribute for literal
SYSTEM ERROR: Can't SET/MAKE instance (0)
Then you should check the version of the interpreter you are running. If it is earlier than 3.0beta3, you are probably looking at this problem.
If you encounter this, there is an easy way to update Gargoyle. Just use a slot-in replacements for your environment and place it inside the Gargoyle directory or application. You will find the gargoyle slot-ins in the download area under Interpreters for you platform. The packages will also include instructions how to apply it in your environment.