We experienced exactly the same issue.
The problem is that Piwik upgrade process did not update the
Filesizes in that file are old (from previous Piwik version), causing all file integrity checks to fail when the system was trying to record details of a visit.
Perform a clean install of
2.15.0 Piwik somewhere else, and once all installation steps are completed, copy the
/config/manifest.inc.php to the original installation. This way filesizes are up-to-date, and the file integrity check will not fail.
piwik_log_visit table did not help as it was handled by the update process.
Re-uploading the files did not fix this. We tried doing this manually, with
wget, using a development beta version, as well as cloning the whole repo and going back to the
2.15.0 stable tag.
The issue was still there, as it seems that
manifest.inc.php is generated only upon new Piwik installation.
If you have any questions, or need more specifics on the installation, let me know.