When the end of year process is run, the account type structure in the "from" year is moved to the "to" year.  ( The description moves as well).For example:

In 2015 the fund was a single fund balance pass thru fund with a Q3 fund balance.  All the R,X,T accounts were 3's. ( R3, X3, T3).
In 2016, the fund became an endowed fund and management wanted to retain the history and change just the fund balance structure.

Thus, an Interest Revenue account that was an X3 in 2015 became an X2 in 2016.  

When end of year closing is run in 2015 to 2016, the X3 structure on the Interest Revenue is moved to the 2016 account, replacing the existing X2.  Although in this instance, this is not what you want to happen, it is important for the GL structure to flow from the prior year.

Normally, to fix the now mis-typed accounts you would run the File Maintenance > General Ledger > Calibrate GL Account Type process.  In some situations it might be necessary to manually adjust the new year.

We recommend that Fund balance structure changes take place after the majority of the activity in the old year is finished so that the end of year closing process won't need to be re-run en masse.