big nate island cannot be completed, after a certain point the game will require you to have a membership to continue, and the diving minigame's timer ticks down too quickly (i assume this is bc the game is now 60 fps, an option to toggle the original and new fps might help with some islands issues until they can be fixed otherwise)
spy island can be completed, i honestly thought that was how the bowtie worked anyway tbh, but certain rooms are really laggy (toupee terrace for one due to the flickering lights)
nabooti island is completable, i had no issues other than the section to get inside the diamond mine, where the minecart dodging section (i assume its supposed to work like the old donkey kong arcade game) was broken due to the minecarts not spawning properly (i think?) they would end up below where they were supposed to spawn and just fall and then disappear. it didnt cause any problems but it was worth mentioning i suppose. the minecart ride worked fine though.
reality tv island is completable, just slight lag and minor visual errors. (voted off contestants would still be there on the screen to begin the next game, the contestants icons would show up around the middle of the screen rather than the top in some games)
skullduggery island is completable, i dont think i had any issues there, just remember to save and quit often bc losing progress on this island is really annoying
DO NOT go to monkey wrench island, you will just get stuck in that plane. i think i have to make a new profile now.