Blocks stop updating one minute after entering the Nether or the End

Gravel/sand blocks in the nether are not affected by gravity, even when manually placed or updated (eg. by destroying a block next to floating gravel). Seems to only happen after spending some time in the nether, possibly related to chunk updates. Reproducible after entering the nether and waiting a while for the world to generate and lava to fall (1-5 minutes).