I have come to the conclusion that if you give the city some generators it might help - as it might be a power problem..........but i aint sure
Try giving it the platforms for it as well - with their loadouts which include teh shield gens etc. I think you will then have it lasting longer (as mine has no problems). You can find them in the system file for that system. Its probs a lack of power to be honest - or that is the best guess (seeing as you haven't posted up what you have in the ini files at all).
Here is a slight hint for you from the mission 13.ini file. You CANNOT just paste these into your files though - it needs "refining"
[MsnSolar
nickname = dyson_generator1
string_id = 10916
faction = fc_n_grp
system = St03
position = 1000, -150, 1000
archetype = dyson_generator
loadout = dyson_generator
label = generator
radius = 0
[MsnSolar
nickname = dyson_generator2
string_id = 10916
faction = fc_n_grp
system = St03
position = -1000, -150, 1000
archetype = dyson_generator
loadout = dyson_generator
label = generator
radius = 0
[MsnSolar
nickname = dyson_generator3
string_id = 10916
faction = fc_n_grp
system = St03
position = 1000, -150, -1000
archetype = dyson_generator
loadout = dyson_generator
label = generator
radius = 0
[MsnSolar
nickname = dyson_generator4
string_id = 10916
faction = fc_n_grp
system = St03
position = -1000, -150, -1000
archetype = dyson_generator
loadout = dyson_generator
label = generator
radius = 0
Note - remove label, change faction = to reputation =, give it a pilot line, make string_id into ids info/name whatever (you don't actually need any ids stuff- but it will appear labled as IDS?. Remove the system line, and then the radius. Give it a behaviour.......ack - sod it, here is a platform - make it look like the platform but with its loadouts and archetype
[Object
nickname = St02_lair_platform09
ids_name = 10903
pos = -1723, 325, -1655
Archetype = lair_platform
ids_info = 10904
pilot = pilot_solar_hardest
loadout = lair_platform02
reputation = fc_n_grp
behavior = NOTHING
visit = 0
Have fun - as that should get ya working