I think the upgrade error is due to the spot check we do to make sure the upgrade script and files are compatible. The version of the upgrade script is defined in installcore.php ... so for 1.1.3 it sets
CURRENT_VERSION = '1.1.3'
Next we check one of the files and historically it is index.php. This involves reading the comment header where we look for the @ version tag and compare that value with what CURRENT_VERSION . this results in 1.1.3 vs 1.1.1 becuase index.php has not changed since 1.1.1.
Historically index.php always changed with each new revision since the forum version constant was set in that file, but in 1.1 we moved that setting to bootstrap.php
So what does that all mean, basically we need to read bootstrap.php and not index.php going forward. In the upgrade.php script we need to make the following change.
// Do a quick version spot check.
$temp = substr(@implode('', @file(BOARDDIR . '/index.php')), 0, 4096);
// Do a quick version spot check.
$temp = substr(@implode('', @file(BOARDDIR . '/bootstrap.php')), 0, 4096);