jm Bitcoin CashL±I knew (ABC) checkpoints were a dangerous way to go the moment I heard of them, as they mess with PoW. Here is a simple explanation of some dangers: https://tinyurl.com/ya8q5llx
https://whatsonchain.com/tx/170684263758821ec620888c47cebb14352f46e8ab140691ce1c9fa6ac88b610