Tried adding new, large resource fields and got an error.
One normal ore and one Angels infinite ores type (center of the normal field).

I got the following error:

The mod YARM - Resource Monitor (0.10.13) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event YARM::on_tick (ID 0)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
    [C]: in function '__index'
    __YARM__/resmon.lua:320: in function 'add_resource'
    __YARM__/resmon.lua:1689: in function 'update_players'
    __YARM__/resmon.lua:1732: in function 'on_tick_internal'
    __YARM__/resmon.lua:1766: in function <__YARM__/resmon.lua:1761>

i just released 0.10.14 that should fix this. looks like an entity was deleted inbetween starting the scan and finishing it. thanks for the report :)

I just had this same error on 0.10.14. It was coal ore, on a different surface (Space Exploration). The problem went away after I ran belts to remove the dropped coal from the ground AND removed a non-functional mod (Where Is My Body, which isn't compatible with SE it looks like). Unfortunately I don't know which actually solved it.

The mod YARM - Resource Monitor (0.10.14) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event YARM::on_tick (ID 0)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__YARM/resmon.lua:453: in function 'scan_current_site'
YARM/resmon.lua:1676: in function 'update_players'
YARM/resmon.lua:1733: in function 'on_tick_internal'
YARM/resmon.lua:1767: in function <YARM/resmon.lua:1762>