I want to bring something to your attention....
I just installed a fresh SMF 2.0.15 forum, and am adding PortaMX 1.54 ecl to it. I started by downloading installation zip from the SMF Mods site and uploaded it to my site.
When I clicked to install, Error in Package Installation was displayed, and the following test actions failed:
5. Execute Modification ./Sources/Load.php Test failed
1. Replace ./Sources/Load.php Test failed
6. Execute Modification ./Sources/LogInOut.php Test failed
1. Add After ./Sources/LogInOut.php Test failed
I then downloaded the installation zip from the download section here (as a test,) and it installs perfectly - it throws no errors when I install. I am not sure if you are the one who is responsible for uploading updated files to the Mod site, but IMO it should be replaced ASAP...