By default, Matomo (Piwik) will truncate Page URLs and Page Titles after 1024 characters (1 Kb). If you are tracking Page Titles or Page URLs that are longer than 1024 characters, Matomo will truncate (cut off) the extra characters. To make sure that Matomo correctly tracks even your long Page Urls and Page titles, edit your config/config.ini.php and add the following:

page_maximum_length = 2048

After making the change, Matomo (Piwik) will track up to 2048 characters in your Page URLs and Page Titles. You may adjust the value appropriately for your use case.