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.
I can remember having this exact experience a year ago when the Bitcoin network was congested, I sent a few Bitcoin and in a few hours, it got reversed back into my wallet due to low fees. And I'm pretty much sure low fees must have been one of the reason why Payment B as explained above could not have been among your confirmed transactions, as it's likely to have been dropped from the mempool due to low fees while waiting for miners to confirm it, since it's obvious miners do prioritize high fees.
While secondly, another factor that I think might have resulted to this might be when the Bitcoin Node has an issue or Network fails to Synchronize. Because when your Bitcoin wallet app or node is not fully synced or connected to unreliable nodes, pending transactions might disappear from the display of the wallet, just as explained above.
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.
What could have caused this is simply because the transaction was rejected by the miner due to low fees, because we all know that Bitcoin miners do prioritize high transaction fees,
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.
Payment A is now confirmed It's in the new block, the resent Payment B is also confirmed It's in the same new block as Payment A and your wallet balance correctly updates showing both 0.2 BTC and 0.05BTC as spent.
Yes, both transaction seems to have been confirmed in the same block, simply because the miner saw that the recent fees for both Payment A and B transactions was now reasonably enough. Since it's obvious miners always prioritize higher transaction fees.