Ugh... only saw this section after posting in the Common Error/Crash section, so bear with me while I edit, copy/past, and move stuff
Playing vanilla C2C V19, came across some issues:
1) The Bomber will not upgrade into the B52 Strategic Bomber. I can build both, in the same city even, but I can't upgrade bomber to strategic bomber despite what the Civilopedia states.
2) The B52 Strategic Bomber won't bomb defenses. I can "Air-Strike" and attack units to my hearts content, but I can't bomb city defenses. This is also despite what the Civilopedia states.
*EDIT* To elaborate, the B52 cannot perform any bombing missions, either of defenses, or of any the other missions allowed under "Advanced Air Bombing": buildings, production, et al. It seems someone flipped a switch under the XML

3) More of a minor annoyance then anything, but once I have access to "Special Agents" I can't build regular "Agent" until I've already got the national limit of 5 Special Agents in play. I can only surmise this is due to a combination of Agents upgrading into Special Agents, and a RoM/BUG/AND setting of not showing replace/obsolete/et al units. Not a major issue, but perhaps Special Agents could be turned into their own breed, with nothing upgrading into them?
4)
*EDIT* Also, would it be possible to add a splash of color or something to either the Railroad or Electric Railroad improvements? Otherwise they are exactly alike in appearance and impossible to tell the difference at a glance of the main map without hovering the cursor over the plot in question and bringing up the tooltip.
5)I'll have to double check, but I believe there were 2 different kinds of early roads that were exactly alike in benefit, but one variant cost 1

to build.
Other than those few items, so far so good. I'm playing on a Huge European map made in the pre-C2C days so I don't have all the new fangled terrain at the moment but otherwise no big issues. Victory Settings are for Diplomatic or Scientific Victory, I'm hoping to push for Science, I'm in the Modern Era at the moment, but due to the land:water ratio being so skewed and starting in Prehistoric, my save game is pushing 3.3MB, and usually I start to have CTD issues around 2.5MB.