Try using inotify

Dockerfile

-FROM alpine:3.10
+FROM alpine:3.15
 
 RUN apk add --no-cache \
-  fswatch
+  inotify-tools
+  
+ADD src/entrypoint.sh /docker-entrypoint.sh
 
-ENTRYPOINT ["fswatch"]
+ENTRYPOINT ["/docker-entrypoint.sh"]

src/entrypoint.sh

+inotifywait -e close_write,moved_to,create -m $CONFIG_DIR |
+while read -r directory events filename; do
+  killall -SIGHUP quasselcore
+done