Ok I tried loading up the savegame.pdb before the 2nd time my constructed infrastructure became unconstructed and the corresponding puzzles became unsolved. I think I loaded it on Thurs or Wed.

Today, the puzzles have become unsolved again! So all in all it happened to me 3 times!!!

Because I load the saved game that I have saved after the 1st time puzzles became unsolved, this time the puzzles that remained solved is #2, #4, #7 & #11. But in the game itself, puzzle #4 & #11 are not solved at all. I'm gonna go soon!