You do both payments one after the other and your wallet immediately shows both Payment A and Payment B as pending. After an hour you refresh your wallet Payment A is still pending but Payment B is gone It's no longer in your pending transactions list and it is not your confirmed transactions or balance.
After refreshing your network on your phone the 0.05BTC you tried to send for Payment B reappeared in your wallet balance making it look like it was never spent You're a bit confused thinking probably there was a network glitch. Then you resend Payment B with a higher fee than before and it says pending immediately.
After an hour You check again.
Payment A is still pending
The resent Payment B is also still pending
Your wallet balance still reflects the 0.05BTC for the resent Payment B as if it's still available even though your wallet says pending. Suddenly a new block is found and confirmed on the Bitcoin network and your wallet syncs up.
Miners rejected the transaction because the fee paid to the network to complete the transaction was lower than the acceptable amount, so the transaction was rejected by the nodes from the mempool. To reduce the congestion of the mempool and to increase the transaction fee, the low fee transactions are rejected from the mempool so that the high fee transactions can take their place. And when the transaction is rejected from the Mempool, the wallet no longer shows pending because the transaction is no longer in the mempool. I think this is what happened to your transaction.
Again your wallet is back through Unspent Transaction Output because the miners rejected it and had to increase the fee again to make the transaction.