Actual bug, in my view: NewGRF settings are not reset (or at least migrated) after upgrading a NewGRF

So I'd just like to call attention to this again and maybe expand on the issue, as I've since had two more reports in the span of about 3 months claiming my NewGRF is broken, when in fact it is this bug causing the issues, and this last time it has genuinely broken someone's game.

In addition to the parameters window not being updated (as described by the OP), any new parameters added by the newer version will simply be set to a 0 value when starting a new game. This can cause major problems if these new parameters are not supposed to ever have a 0 value, like in my case, it will completely break the gameplay leading to reports that the NewGRF is broken (which it now is). Normally this should never be possible, as newer versions are set as incompatible, but as shown here the "upgrade" button disregards that completely allowing users to unknowingly break their own game.

Worse yet, this effect is persistent, meaning restarting the program will not reset the parameters for subsequent new games; the offending NewGRF must be removed from the list (including any presets) in the main menu and re-added manually to fully resolve the issue, which is not an obvious solution. In this case the upgrade button effectively "permanently" breaks the NewGRF configuration until the user manually resets it, which renders the upgrade button not only useless, but even dangerous.

In case it may be useful, I've attached a .zip which contains two NewGRFs to help show the issue: an older version, and a newer version which is incompatible with the older one and has two new parameters added to the bottom of the list which should have a minimum possible value of 1.

wasteland_0.7.zip

I have seen Iron Horse grf bug reports in Discord that appear to be caused by the behaviour described by Andrew350. i.e. I bumped incompatible version between 2 releases, but players with older savegame appear to have been able to upgrade to the newer release, breaking their game in the process. This isn't confirmed though and when I asked for more info, it wasn't provided.