Sudden Errors with "rlNavigator.class.php" being corrupted

Recently, my flynax frontend became inaccessible with the dreaded white space and with the error message "public_html/XXXXXXX/includes/classes/rlNavigator.class.php is corrupted".

I have searched the forums and came across posts by the support team pointing to rlNavigator.class.php not being compatible with my host's PHP version (5.4.36). A certain post included a file for rlNavigator.class.php which I downloaded and uploaded to the /includes/classes folder. This fixed the problem but several days later, the same problem recurred and was resolved by uploading the same file.

I checked other posts which attributed the problem to either Zend Guard or IonCube Loader not being installed. Both are installed in my host.

Does anyone also encountered this problem? Support, what do you think might be the problem and how can I resolve this?

Thank you in advance.

Noel