in my case there wer 2 PARALELL running php-fpm AFTER installing php84...

root 156309 0.0 1.6 564712 29428 ? Ss 08:54 0:00 php-fpm: master process (/etc/opt/remi/php84/php-fpm.conf)

apache 156311 0.0 2.2 570264 40084 ? S 08:54 0:00 php-fpm: pool www

apache 156312 0.0 2.1 570108 38104 ? S 08:54 0:00 php-fpm: pool www

root 160616 0.0 2.2 734516 40792 ? Ss 10:05 0:00 php-fpm: master process (/etc/php-fpm.conf)

apache 160618 0.0 1.1 739560 20668 ? S 10:05 0:00 php-fpm: pool www

apache 160619 0.0 1.1 739560 20668 ? S 10:05 0:00 php-fpm: pool www

...

so I have to

systemctl disable php-fpm

service php-fpm stop

and

service php84-php-fpm restart

And after it... been solved all my problems 🥴

👍