UK Puzzle Association

I was looking for old Taca puzzles and found the TVC 20 contest from 2016..
https://logicmastersindia.com/lmitests/?test=TVC20

The rules look normal, but both of the puzzles break when I try to solve them.
For example, in the top-right corner of this puzzle:
- 12 can't go in a corner, so shade the corner cell
- 6 can't go on the edge, so shade the edge cell
- 6 is not the same as 14, so shade the 14 cell
- but now we can't shade the 12 cell (because that makes a shaded 2x2) and we can't leave it unshaded (because it has 3 shaded cells next to it).

What am I doing wrong?

From the forum for that test:
https://logicmastersindia.com/forum/for ... t=1#M22255
"I think rules of Taca need some clarification. From puzzles in the actual test, "first seen unshaded cell" should be replaced by "first seen cell that is neither shaded nor clued"."

To clarify, this round's taca does indeed follow the rule that the clue must be placed in the first unshaded cell, contrary to the last time taca appeared.