I think the problems are related to the way the map is installed and selected.
Example: 860map is installed and running fine, new 880 map get's added and activated - all fine device boots and you switch to the new map in the menu.
860map is installed and working, new 880 is added and the old map deleted - many devices will hang and stop to work normally.

You might wonder why but it is simple to explain:
Inside the ttgo.bif you can see what mapis currently in use, but it is recreated at each boot anyway.
More importantly you also have the file CurrentMap.dat which holds the actually info which map is installed and in use.
Also there is the file CurrentLocation.dat which holds the info where the TT had the last sat reception before turning off.
So when you start a TT with the old map deleted and a new map added some devices only check for the location of the map as defined inside the CurrentMap.dat - which won't work if the map folder is different and/or the map is different in name. This in return can cause the device to hang and become inresponsive, not even reset or Clear Flash will help.
Similar thing can happen if your old map was for example a Europe map with the last use in Europe. If you replace the EU map with a US map (and have not got a proper sat fix before) the TT can't position you on the new map and can freeze too.

IMHO the safest way to avoid problems when installing a new map is to delete the CurrentMap.dat and CurrentLocation.dat in the root after the new map is installed and activated and before you start the TT with the new map.
Might also help once you got the problem already