Hi guys, this one has been around for a while, trigger for it to fail/succeed identified here so this is helpful:

What should happen: When a more advanced trade tech is researched all existing watchtowers auto-upgrade to the new, improved version.

Issue: Sometimes this does not happen. The trigger for it to fail seems to be if ALL watchtower foundations in a region have towers, in that case no upgrade occurs. If some but not all foundations in a region have been built upon the upgrades are applied as intended.

To reproduce: Load the attached save and press next turn when research of Enlightened Trade will complete. In the two regions where one tower site has been left empty, all towers upgrade to Remotuscopes. In the region where all tower sites already have towers those have not upgraded and remained as Lookouts.

https://www.dropbox.com/s/wrdo0ievtn6ik4r/WatchTowersBugTrigger.zip?dl=0

Hope I've done that correctly, a bit out of practice ><