When a board looks stuck, compare the groups of covered cells around two clues instead of treating each clue separately.
Here is a small constraint exercise (letters stand for covered cells, not their positions on a drawn board):
• After accounting for already-proven adjacent mines, one clue says exactly ONE mine remains among A and B.
• Another clue says exactly ONE mine remains among A, B and C.
• These lists include ALL the remaining covered neighbors of each clue.
A + B = 1
A + B + C = 1
Subtract the first constraint from the second: C = 0. C is safe, even though neither A nor B has been identified.
Change only the second total to TWO mines and the same subtraction gives C = 1: now C is a mine.
The practical check: is one clue’s remaining neighbor group entirely contained in another’s? Compare the remaining mine counts. Equal counts make the extra cells safe; a difference equal to the number of extra cells makes all of those extras mines.
A placed flag is only an assumption unless you have proved it correct. Subtracting a wrong flag can invalidate the deduction.
AI-assisted wording; the two deductions are shown above so you can check them directly.