I figured out what is the issue with diplomacy tab, however it might be difficult if not impossible to fix it unlike the glitch with artifacts list and tournament quests. Unlike most of other things, unlocked characters are not imported/exported through save menu. If you export/import game between different devices, you will need to unlock characters again. You can, however, export game's save just before doing action that would unlock character - and import + do it before importing 'proper' save. I guess that explains why I had Sebastian available after starting game from 0 again.
About diplomacy tab issues: If you inspect the broken Artifacts / Mission menu, you will find ul element with ID "diplomacy_list". The very first element is list that is container for artifacts/unassigned missions. In Chrome browser, in my case it appears to have fixed value of height:64px - which is only enough for a header. Changing the "64px" value to "auto" or anything reasonable should make lists visible until you switch tab - but should be enough to actually see what artifacts you have and/or what is the mission. Apparently similar issue happens for characters, but I got only one at the moment.
There appears to be some issue related to diplomacy tab currently. On Google Chrome, only name of only the first artifact is shown. Same with Tournament related missions, only the title, no conditions nor rewards. They are however visible in the page's source (could they be pushed under background, perhaps?)
Loading game on Firefox seems to be solving this issue, yet on that browser, the Characters tab is missing. And like, completely, including page's source.
Only issue I have about this part is... FPS. For some reason, I get slideshow, compared to the smooth SCGMD3. Though, with the support for Flash ending, I wonder if there will be ever SCGMD5, perhaps in Unity or HTML5 so we can enjoy the game series without any issues ^^
After playing CW, CW2, CW3 and PF:E, I returned to this small game, out of curiosity, searching maybe for hidden lore parts. Now, especially after final mission here... yet again, I start to wonder about the CW3, it's ending. While I don't want to spoil anything, I can't help it but wonder about the 'Simulant' concept. Was Lia testing future choices of Abraxis... or trying to understand past ones :P
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 "SCGMD4"){kind=icon}
 "Creeper World 3: Abraxis"){kind=icon}