Dunno if this is a known bug, There is a bug where if you click off an item to research it and click back on it it greys out the Unlock research button (i made certian it was one of theo nes i could research. also a ?bug? was for a while after researching Arid reclamation (or whatever it was) i was unable to build any on the Arid tiles on earth, i haven't been able to replicate it on any of my other games just one of my old conquest wins 

Also a nice QoL implementation is being able to select more then one of the same improvement and being able to queue them all up at once for upgrading.