It's now impossible to sell provinces outside of your own coring range (whereas it should check the coring range of the potential buyer instead).
I just experienced this myself, hugely irritating.
If you are trying to sell (give away) a province to an ally that they completely surround but seemingly are unwilling to gain control of during the war, take control yourself and then demand as a war prize to give to them later you will be in for a massive nasty shock, as the blurb now reads "too far away for your XXXX nation to core this province" or somesuch.
A major bug.
In my personal example I'd decided to make Hungary my Ally as more than one is a pain due to the pointless never ending wars Allies always start, in this case Serbia was one of those wars. they completely surrounded the two disjointed provinces, and as usual, declared a war upon them then then brought half the planet into it. Fed up with this level of spam I occupied both provinces, annexed Serbia and then discovered that as they had no connection to my Capital in Lithuania, and was thus unable to core them, I couldn't actually give them away to Hungary.
All of this whilst trying to deal with the every-10 second random event spams you get.
I also noticed the colonies that were getting built in the 1550's were quickly being converted into colonial nations and actually blocking off the interior of North America in that great game-breaking idea thrown into a patch (don't waste your time colonising any longer) so I decided to look at what few bits of the game didn't spam me or weren't yet broken (Trade, most diplomacy, Colonisation and exploration and The Curia are all broken or too spammy) and hit upon sticking it out in Europe to try the last working part of the game, and so simply tried to just be friendly to my neighbours whilst colonising Siberia (I changed the defines.lua to prevent a spam conversion of some of the provinces into a colonial nation and thus preventing me from ever reaching the coast). The "border tension" model soon put paid to me trying to be friendly however.
In my previous (of 3 games) games I was spammed with a random event roughly every 10-15 seconds as well, so, so utterly irritating, back before the current patch, "Improved Fortifications" spammed me about every 10-30 seconds (end game about every 15 seconds), in this current version it's about every 5 minutes, but spam heretical conversions have now taken over as the greatest constant pop-up pains amongst the "randoms". For about 150 years, at any given time 2-4 of my 5 missionaries were permanently tied up in re-conversions, the counter-reformation has now just ended to I hope that spam has now ended.
If I know one thing about Paradox as a buyer of the original EU, since that game they certainly know how to take great idea's and then smash them to bits with random event spams, and now in the 4th incernation of EU, force the player to spam themselves (light shipbuilding, The Curia, making the mistake of accepting an minor Ally (who then always drags you into a war with the Planets most powerful coalition to "show superiority", or automatically forcing you into a war against another Ally which then costs you their goodwill and a -25 prestige hit for refusing) etc, etc.
What was HOI3 about? 10,000 provinces and a command system so bizarre even the computer got confused.....
Vicky 2, compete with an economic system that never worked from day 1 and never got fixed either......
EU3 where the entire Western World went Protestant within a year........
La-de-da. Goodbye Paradox, AGEOD here I come.