Occurrence throwing error at line 1 - hash/pound key seems to be the trigger

[onemaxsim]

Hi, I wrote a rule that - if it was working as expected - warns me if it finds a lone level 3 subheading in my Markdown doc. Here is the rule:

extends: occurrence
message: 'A lone h3 is detected. Lone subheadings indicate that the content is insufficient or has a weak structure.'
level: warning
scope: raw
min: 2
token: '^### '

I also have the same rule but for level 2 subheads. I tested it with the following Markdown:

# Title

An overview para.

## A subheading 2

An intro para to this section.

Another para.

### A subheading 3

Another one.

And a final one.

Buggy behaviour: Vale shows me a warning for line 1 of the code, and not for lines 5 or 11, which is where the subheadings are.

Further test: I changed the token to: 'you', and edited the Markdown so it contained the word 'you' twice. This time, the occurrence check worked -- it did not throw a warning, which is expected behaviour given that it's looking for at least two occurrences of the token. So, I believe the problem is to do with the hash key.

Why is this happening?
Is occurrence broken?
Or is my rule not correctly formed?

Thanks,
S.