The worst desync I have expreicenced

Me and my friend were both playing on pc via Steam. We needed to alt+tab for the next levels to load, the regular, yeah.
We get to Tide Pool and the whole game falls apart. I see, that my friend dies after some time in the level, BUT HE ACTUALLY DIDN'T DIE IN HIS GAME. THEN he sees that I randomly go to the water pool at the bottom of 4-2 and waste our Ankh, WHEN I ACTUALLY DID NOT DO THAT AND WAS JUST FINE. I was going back in the level to get a pet so I could heal my poison WHICH MY FRIEND DIDN'T SEE I HAD. I leave the level to go to 4-3, while my friend is still in 4-2. We both died in our own games quickly after.

I really hope that something gets done to this problem. I have expreienced lag and desync before but this is on another god damn level. Makes me honestly not want to play the game with friends anymore.
Can we form a support group for people who have suffered from Spelunky 2 desync or something?