Unable to write *.sieve files while Dovecot is running

I noticed lately that I can no longer modify *.sieve files while Dovecot is running. Write operations appear not to be permitted anymore:

$ echo >> example.sieve zsh: permission denied: example.sieve

Text editors like vim cannot write either. Since I used to be able to modify Sieve source files on the fly, I am wondering if the behaviour I see nowadays is intentional?

Doveconf reports the following versions:

# 2.3.14.1 (9f0cfb6426): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.14 (1b5c82b2) # OS: Linux 5.17.1-gentoo-r1-x86_64 x86_64 Gentoo Base System release 2.7

-Ralph