At any time, after starting the game hovering the mouse over the replace signals button causes the game to crash.
Running the game at "-debug 2" produces nothing valuable:
Warning: fabrik_t::rdwr(): Factory at (1148,702,-5) requested producer for textile but has none!
Warning: fabrik_t::rdwr(): Factory at (1148,702,-5) requested producer for flour but has none!
Warning: fabrik_t::rdwr: Mismatch of input slot count for factory Market at (1148,702,-5): savegame = 6, pak = 4
Warning: fabrik_t::rdwr(): Factory at (6320,812,-3) requested producer for textile but has none!
Warning: fabrik_t::rdwr(): Factory at (6320,812,-3) requested producer for flour but has none!
Warning: fabrik_t::rdwr: Mismatch of input slot count for factory Market at (6320,812,-3): savegame = 6, pak = 4
Warning: fabrik_t::rdwr(): Factory at (701,115,2) requested producer for textile but has none!
Warning: fabrik_t::rdwr(): Factory at (701,115,2) requested producer for flour but has none!
Warning: fabrik_t::rdwr: Mismatch of input slot count for factory Market at (701,115,2): savegame = 6, pak = 4
Warning: karte_t::load(): loaded savegame from 2/1780, next month=12582912, ticks=8402369 (per month=1<<22)
Segmentation fault (core dumped)
As ex-15 is still very much WIP, I'd call this low-priority and unique to my system if no one else can replicate this.
Apologies, it's the "Reassign signals" button. I've attached the image for it from the "Special construction tools" tab.
Yes, it is in demo.sve. I would say this is an isolated case and once public testing commences, I can see if it persists.