I have been trying to figure out what I did different so that these odd things started to turn invisible.
That's when I remembered that I started doing aiding manually (by visiting the city, finding an available VF building and motivating/polishing it) to get VF goods!
I tested it today and I believe this to be the reason. I say "believe" because it is very difficult to find where the bug is appearing.
In my first try I couldn't find any invisible windows or items and decided to continue with my polivation business. That's when I saw or rather didn't see the coin and the 1 VF good floating up. Even though I had motivated a building I could not see the coin and the good.
Refreshed the game and went on with visiting cities.
This time the background of the floating coin disappeared.
Refreshed the game again. In my third attempt, I found the bug in the town hall window just like this one
The trader was similar
The guild window however was a different story.
When first opened, looked like this:
Then after clicking profile it showed the normal profile page
But when I clicked the "members" tab, it started doing weird things.
First click, I got 6 tabs. The tabs doubled. Second click tabs are now 9 and so on..
After closing and reopening, it starts again with a null tab just like above and everything is repeated.
So, in short this bug is related to manual aiding and/or collecting VF goods through aiding.
Haven't tested if the same happens after aiding a different era building so I hope someone can do that. (with and without collecting goods)
The actual problem is that the bug is not consistent. It appears in different manners and it is hard to detect it since almost everything needs to be checked (including aiding further to see if the coins etc are visible or collecting productions to see if the icons appear properly)
The only consistency is that it turns things or part of things invisible.
Edit: The quest window also froze (the lower two) during this process so that too may be related to this bug.
EDIT 2: Now I am less sure about the aiding theory.
It is possible that visiting a player's city or visiting+doing an action may be the trigger.
I just visited a city, checked the tavern and upon returning the inventory window turned half invisible again.
I refreshed, revisited the city and checked the tavern, same issue with inventory happened again.
But on the third try, the bug appeared somewhere else. So it the inconsistency continues.
1.131.e00be7fbfc (06.07.2018 11:13), Tiraje (96405), zz1, en_US, WIN 30,0,0,113, Windows 10, Chrome/67.0.3396.99, 1920x947, OpenGL (Baseline Extended) (336 MB VRAM)