Running version 0.15.13 of factorio and the latest version of the mod. I tried to upgrade a group of belts and splitters.

Screen capture of error: http://imgur.com/a/AxOhD

Also clicking a blueprint on the upgrade blueprint button doesn't work to upgrade the items in the blueprint.

Update: I removed some other mods and I can upgrade existing entities again using the upgrade planner. One of the mods I removed was Orphan Finder. That may have been the cause of the problems here.

Update 2: Just kidding. I can upgrade just fine if I upgrade only belts. Any other item in the selection area causes the mod to crash.

Update 3: I can upgrade belts and splitters. Underground belts and other entities cause the game to crash.

Hi I have the same problem.
My game version is 0.15.13 and mod version 1.2.17.
The Mod works fine if I only upgrade belts. If I want to ubgrade other items the game crashed.

Update1: The mod crashed only when I want to upgrade underground belts. Splitter, belts and inserter worked fine.

The mod crashed for me if a roboport was in the selection area, even if it wasn't slated for upgrade. Which leads me to believe that any entity other than belts or splitters will cause a crash.

Underground belts are causing it to crash on my game ( 0.15.13 )
Error below:

Error while running event upgrade-planner::on_player_selected_area (ID 49)
LuaEntity doesn't contain key 1.
stack traceback:
upgrade-planner/control.lua:713: in function 'player_upgrade'
upgrade-planner/control.lua:692: in function 'on_selected_area'
upgrade-planner/control.lua:662: in function <upgrade-planner/control.lua:661>

Same as above. Underground belt upgrading from yellow to red on 0.15.13

Error while running event upgrade-planner::on_player_selected_area (ID 49)
LuaEntity doesn't contain key 1.
stack traceback:
upgrade-planner/control.lua:713: in function 'player_upgrade'
upgrade-planner/control.lua:692: in function 'on_selected_area'
upgrade-planner/control.lua:662: in function <upgrade-planner/control.lua:661>

I just upgraded to the latest version of this mod (1.2.18) and no longer have the issue. Thanks!

Updated to the latest version and still crashes when trying to upgrade underground belt. I am trying to go from red to blue if that helps at all.

Edit: This mod no longer causes problems, thanks for the quick response!