Grav-plugin-admin: Web UI Says "Cron Not Available" Yet It's Working

I've setup my own Docker image for running Grav, but there's just one issue that I can't seem to figure out, and it is that the Web UI says that Cron isn't available, but yet it seems to be working just fine from what I can tell.

This is the warning that I'm trying to fix:

I have the crontab running under the nginx user, which seems to work just fine:

Using the CLI, I can verify that nginx has the correct crontab:

And just to see if it would make a difference, I added it to the root user as well:

... But it still shows the same warning in the Web UI.

The CLI also shows that the backups are being run:

I'm not entirely sure what else I can do to see if I can get this warning fixed.

My Dockerfile:

FROM nginx:stable-alpine
LABEL maintainer="William Miceli <[email protected]>"
USER root

ARG GRAV_VERSION

# Install Dependencies Needed For Grav, With Optional Modules To Help With Performance
RUN apk update && apk add --no-cache \
    dcron \
    php7 \
    php7-curl \
    php7-dom \
    php7-fpm \
    php7-gd \
    php7-json \
    php7-mbstring \
    php7-openssl \
    php7-pecl-apcu \
    php7-pecl-yaml \
    php7-session \
    php7-simplexml \
    php7-xml \
    php7-zip

# Configure NGINX For Grav
ADD https://raw.githubusercontent.com/getgrav/grav/c381bc83040e00c9a8ebe91ac3bda5fe0c217197/webserver-configs/nginx.conf /etc/nginx/conf.d/default.conf
RUN sed -i 's/root \/home\/USER\/www\/html/root \/var\/www/g' /etc/nginx/conf.d/default.conf \
    && sed -i 's/fastcgi_pass unix:\/var\/run\/php\/php7.2-fpm.sock;/fastcgi_pass unix:\/var\/run\/php-fpm.sock;/g' /etc/nginx/conf.d/default.conf \
    && sed -i 's/#listen 80;/listen 80;/g' /etc/nginx/conf.d/default.conf \
    && sed -i '23cuser = nginx' /etc/php7/php-fpm.d/www.conf \
    && sed -i '24cgroup = nginx' /etc/php7/php-fpm.d/www.conf \
    && sed -i '47clisten.owner = nginx' /etc/php7/php-fpm.d/www.conf \
    && sed -i '48clisten.group = nginx' /etc/php7/php-fpm.d/www.conf \
    && sed -i '49clisten.mode = 0660' /etc/php7/php-fpm.d/www.conf \
    && sed -i 's/listen = 127.0.0.1:9000/listen = \/var\/run\/php-fpm.sock/g' /etc/php7/php-fpm.d/www.conf

# Setup Cron
RUN (crontab -u nginx -l; echo "* * * * * cd /var/www;/usr/bin/php bin/grav scheduler 1>> /dev/null 2>&1") | crontab -u nginx -

# Prepare Grav Files
RUN mkdir -p /var/www /usr/src/grav/user \
    && apk add --no-cache ca-certificates \
    && apk add --no-cache --virtual .install-dependencies unzip wget \
    && wget -P /var/www https://github.com/getgrav/grav/releases/download/${GRAV_VERSION}/grav-admin-v${GRAV_VERSION}.zip \
    && unzip -q /var/www/grav-admin-v${GRAV_VERSION}.zip -d /var/www \
    && rm /var/www/grav-admin-v${GRAV_VERSION}.zip \
    && mv -v /var/www/grav-admin/* /var/www \
    && rm -rfv /var/www/grav-admin \
    && apk del .install-dependencies \
    && chown -R nginx:nginx /var/www \
    && mv -v /var/www/user/* /usr/src/grav/user

COPY /entrypoint.sh /

EXPOSE 80
CMD ["/bin/sh", "/entrypoint.sh"]

Git repo

Thank you for your help!!