Hi Steve,
I don't know anything about the S-Variable/input table in TANE SP4, but if this is the same as other assets that require an input table, there are timeout limits set in TANE SP4 and the newer Trainz versions that will cause rules to stop working if they wait too long.
On downgrading an install. You really don't want to do that because going back to a previous version will mess with your content, especially routes you have modified due to the changes in the data formats. Things look the same to us but underneath there are changes to the files, sometimes subtle changes, to help with efficiency and performance. These changes can cause your downloaded data to not load properly if at all.