You're going to have to be a bit more specific as to what is inaccurate in the maps. I have the upmost confidence in the European maps from 800 onward;
Well, it's true that pre-800 maps are particularly problematic compared to the others, but taking the example of 1000, which seems to be based on a map I did for the same period.
Generally, the problems are that you're using overly complex and ultra detailed borders that have no real reality to be based on : it's particularly obvious in Eastern Europe and Northern Asia, as even specialized atlases as "Atlas of Central Asia" tries their best NOT to pull this sort of things. It seems pulled out of nowhere, really.
It's not just there, and can be seen in Spain too (the County of Porto northern border is arbitrary, granted, but it's why I used a simple map and not an even more arbitrary complex line without much to be supported) or Navarra.
Tiwanaku and Wari are merged for some unknown reasons, and there's a continuity of chiefdoms between peru and Panama (withut much grounds for) while Mississipian cultures (known for their high degree of development) are absent. Oh, and Asanazi's cultural area looks like...well, it doesn't looks like anything, really.
Africa is, I'm sorry to say, a disaster. I'm using sources such as UNESCO's general history of Africa and it simply doesn't fit anything. Nubia is frankly a catastrophe in itself. I shudder to think whoever drew this used as sources. And in the same time no Swalili, no proto-Zimbabwe. It's like I reverted 10 years ago when African polities weren't represented on worlda, but with worse borders.
Note that Arabia isn't much better and looks like someone just guesstimated the borders.
Central Asia and India makes literally no sense at all : I drew the map that was used as a base, and I can't figure out what's representing what. I'll pass on the disappearance of Volga Bulgars or the anachronistic depiction of Rus'
SOuth-East Asia is better, but frankly that's not a challenge : the author of the map actually, for real, used a modern Vietnamese map as base. Nanzhao was literally MOVED out of Nanzhao. It's like the problem you pointed with Czechia, only on a much, much larger and obvious scale. I agree that I badly rended Nanzhao myself, but at least it was where it's supposed to be, not going into vacation elsewhere.
Liao and Wia states are just bad, so no need to cover this too much, but you'd think that one could have figured Japan without giving up and coloring the whole island.
In fact, it's telling that whoever took my map to redo...this didn"t really felt like working and doing an actual job : years ago, I made this joke to
@Alex Richards and
@Lord Hastur of Carcosa that I could put a dong-shaped country on the map and nobody would be the wiser. Guess what's on the Kola peninsula
in my map, and
on the one in this thread? This alone makes me thinks that there was no study or research involved at all.
I'm not claiming some special knowledge or skill, but people I worked both there and outside this board on map-making know that I can take great lengths to be sure what I draw is a fair enough representation (that includes digging down to find archeological sources for ancient and medieval maps) and hunting informations. Again, I don't claim at all it makes my work unattackable or perfect (if anything I want to redo them everytime I put my eyes onto it). But I don't think the work on these was really serious : maybe some of the issues come from your choices of coloring and abandon of outlines and shades, granted, but I think the author simply didn't do his job very well on the larger scale (altough they certainly got good ideas for Amazon basin and trying to represent inner politics of Rus')
If you have feedback on other areas of the world in the ancient and medieval maps, I'd love to hear it, but it needs to be specific so that I can actually address the issue.
Frankly, I'd be more comfortable redoing these, it would be easier eventually.