Have you looked at the line of code that it relates to?
It is this line here that it can't find the state of:
if ( $rucss_status['disable'] ) {
Which is part of this block:
$css_section_helper = [];
if ( rocket_maybe_disable_minify_css() ) {
// translators: %1$s = type of minification (HTML, CSS or JS), %2$s = “WP Rocket”.
$css_section_helper[] = sprintf( __( '%1$s Minification is currently activated in <strong>Autoptimize</strong>. If you want to use %2$s’s minification, disable those options in Autoptimize.', 'rocket' ), 'CSS', WP_ROCKET_PLUGIN_NAME );
}
if ( $rucss_status['disable'] ) {
$css_section_helper[] = $rucss_status['text'];
}
Have you got Autoptimize running? If so, turn it off and see if the issue is gone or if it still repeats itself.
You might have already read this, but thought would mention it.
Can you use WP Rocket and Autoptimize together? We'll explain how it works and show you how to set up Autoptimize with WP Rocket.
wp-rocket.me