When using /execute in <dimension> to teleport between dimensions (such as running the command /execute in minecraft:the_overworld run tp @s ~ ~ ~ while in the Nether), potion effects will disappear for around 10 to 20 seconds and will not affect the player during that time. This appears to work with any potion effect, but it is most noticeable using an effect with some sort of visual indication of it working, like levitation, blindness, or nausea. This bug does not occur when using a Nether or End portal, only using commands. The timer for the potion still counts down while it is disappeared.

Steps to Recreate:

1. Create a new creative world with cheats enabled
2. Give yourself a potion effect, either by drinking a potion from the creative menu or by running a command such as /effect give @s minecraft:levitation 90 1 true
3. Teleport yourself into the Nether using a command such as /execute in minecraft:the_nether run tp @s ~ ~ ~
4. After arriving in the Nether, the potion effect will appear to have been removed, but will reappear after 10-20 seconds and begin to affect the player again.

Link to Video with Bug:

https://streamable.com/re4vx