There are a number of issues appearing in the logs.

This one is hanging the wheels of the 'Files tab':

PHP Notice: wpdb::prepare was called incorrectly. The query argument of wpdb::prepare() must have a placeholder. Please see Debugging in WordPress for more information. (This message was added in version 3.9.0.) in \wp-includes\functions.php on line 4231
PHP Notice: wpdb::prepare was called incorrectly. The query does not contain the correct number of placeholders (0) for the number of arguments passed (1). Please see Debugging in WordPress for more information. (This message was added in version 4.8.3.) in \wp-includes\functions.php on line 4231

Fixed it like this:

plugins\integrity-checker\src\Tests\Files.php line 384:
"WHERE l.id IS NULL AND f.deleted IS NOT NULL;";
to this:
"WHERE l.id IS NULL AND f.deleted IS NOT NULL AND f.found > %d;";

These two are giving errors in the 'Upgrade' tab:

PHP Notice: Undefined variable: scanType in \plugins\integrity-checker\src\Admin\views\ChecksumScanResults.php on line 24

PHP Notice: Undefined variable: id in \plugins\integrity-checker\src\Admin\views\Upgrade\column.php on line 67

Just masked both variables to suppress the notice:

line 24:
<div class="scanStatus <?php echo @$scanType; ?>" style="display: none;">
line 67:
<a target="_blank" href="<?php echo $link; ?>" <?php echo @$id ?>

EDIT:
Unfortunately, there are other issues appearing now in the 'Files' tab:

failed to open stream: Permission denied in \plugins\integrity-checker\src\Tests\Checksum\FolderChecksum.php on line 203

PHP Fatal error: Uncaught Error: Call to undefined function WPChecksum\posix_getpwuid() in \integrity-checker\src\Tests\Checksum\FolderChecksum.php:213