Since nothing else has worked, here's what I'd suggest:
1. Install the UpgradeMODX extra in Package Manager.
2. Set your settings_version System Setting to 2.6.5-pl
3. Use UpgradeMODX on the main dashboard (click on the MODX logo) to "upgrade" to 2.7.0, then another upgrade to 2.7.1 (also using UGM).
That will give you fresh versions of all MODX files, plus any DB updates you might have missed in 2.7.0, and it will clear the cache files.