I have two DAP-2553 with FW 1.12 and thought to give the latest 1.20 FW a try.
Update went without any issues but then I found that none of the setting can be persisted any more.
In the admin GUI it looks like your changes took effect but when you restart the AP all changes are gone.
I reverted back to 1.12 and everything returned back to normal
Not much help from D-Link support unfortunately...
