1. Display failure after GPS Start Test issue

First major issue was a software failure after an auto activation of [Start Test] in [GPS] menu. At one point, during a DMR QSO, a GPS test was started and, in the end, the device was restarted. After restart, the display looks like in the picture below:

Basic radio functions were working perfectly, meaning receiving and transmitting. Also, switching between VFOs or programmed channels were not affected.

The GPS function was disabled and, after accessing the transceiver with the CPS software, I found that the APRS menu had disappeared.

As always in such situations, the first thought is to perform a factory initialization, which for AT-D878UV meaning to power-on the transceiver while the PTT and PF1 buttons are pressed simultaneously. Unfortunately, this procedure did not work, the portable starting always with the main booting sequence.

UPDATE: Meanwhile, I found how can be reset the radio if the above procedure doesn't work. You can read about it on http://members.optuszoo.com.au/jason.reilly1/868mods.htm and consists in <Startup Reset> option, available in the CPS software, in <Optional Settings> dialog and <Power-on> tab. If you have problems with the [PTT + PF1] buttons combination, put the mentioned option to <On> value, write the configuration to radio, wait the operation to be complete successfully, then power-off the transceiver. After reboot, continue with the standard procedure for factory reset.

Other workarounds, like unplug the battery or clearing the configuration using the CPS software, have failed. In that conditions, the only normal action was the upgrade from the initial software version (1.10) to the latest one (1.12). It worked perfectly, without any headaches, including the final initialization (PTT + PF1 button). Also,

But, please note that, after enabling again the Start Test in GPS menu, the test was again started automatically, this time without affecting the transceiver. So, while I'm not very sure how useful is this feature, I recommend to keep it disabled.

2. Incorrect placement of PTT in dual VFO screen

The scenario is the following: you are in the dual VFO screen and the main screen (bigger fonts) is set to APRS frequency for periodic beacon updates, but could be any other simplex or repeater channel. The sub-channel (smaller fonts) is set for listening on another frequency (a local UHF repeater, in the pictures below).

If both channels are in idle state (no RX signals, no TX), when the PTT is pressed, the TX state is applied to the main VFO. In our case, to the APRS frequency. The PTT could be the button or a software activation in case of periodic beacon or a remote activation if the transceiver is connected with a computer.

The issue occurs when the sub-channel begins to receive a radio signal and, at one point, the PTT is activated. Normally, this PTT should be applied to the main channel (APRS), but, as you can see in the bellow images, it is applied to the sub-channel.

I checked with a secondary station and the audio input is placed on the sub-channel, instead of the main one, so you have to pay attention in order to not disturb conversations on the sub-channel. A very good measure would be to set the <Busy Lock> option to <Busy> value on all your configured channels, but, unfortunately, it doesn't work. In that conditions, turn off the sub-channel and, again, watch carefully your display before push the PTT button.