I decided to paste the FEN from one of my games here into one of my PGN/FEN/EPD viewers. One viewer would not accept the position because it seems to be fairly strict about adhering to the PGN standard.
Namely the castling rights should be orderd kingside before queenside: KQkq instead of QKqk.
Not a big deal, because my other programs don't seem to care.
Relevant portion of the PGN Standard:
18.104.22.168: Castling availability
The third field represents castling availability. This indicates potential
future castling that may of may not be possible at the moment due to blocking pieces or enemy attacks. If there is no castling availability for either side, the single character symbol - is used. Otherwise, a combination of from one to four characters are present. If White has kingside castling availability, the uppercase letter K appears. If White has queenside castling availability, the uppercase letter Q appears. If Black has kingside castling availability, the lowercase letter k appears. If Black has queenside castling availability, then the lowercase letter q appears. Those letters which appear will be ordered first uppercase before lowercase and second kingside before queenside. There is no white space between the letters.