Problems with paragraph characters in SASL passwords?

[Binarus]

Dear all,

I am very happy with Cyrus imapd since many years. I am using it to host
all IMAP mail boxes of my company. I am using SASL and its tools (mainly
saslpasswd2) for password management. The primary IMAP client in the
company is Thunderbird.

Recently, I have decided to replace all IMAP passwords by longer ones.
While this worked in the vast majority of cases, there were several
mailboxes where Cyrus / SASL refused the connection with the new
password. I have lost several hours of debugging this until the
following turned out:

As soon as the password contained a paragraph character ("§"), Cyrus /
SASL refused the connection due to a wrong password even if the password
was entered correctly into Thunderbird's password dialog. This happened
with Thunderbird 52.1.1 and Cyrus imapd 2.4.16 (as shipped with Debian
wheezy).

My question is: Is there a known problem with paragraph characters in
SASL / Cyrus passwords, or does Thunderbird cause that problem (for
certain reasons, I haven't been able to test other clients yet, and
googling for some hours also did not lead to anything)?

Thank you very much in advance,

Binarus