this is kind of normal , when page is cached , so is that widget , so it retains the information the moment it was generated
a possible solution is use ESI , if you can make it ESI shortcode or ESI widget
e.g https://wp-statistics.com/resources/shortcodes/
you can try , for example , change
[wpstatistics stat=visitors time=today]
to
[esi wpstatistics stat=visitors time=today ttl="0"]