If the player has an ambient level 2 effect (possible in survival via the beacon) and gets inflicted with a level 1 effect of the same type that isn't ambient, the level 2 effect will no longer be ambient.

To reproduce:

1. Create a beacon that gives a level 2 effect
2. drink the level 1 potion
3. the level 2 effect will no longer be ambient (until the beacon reapplies the effect

Alternative method:

1. run

   /give @p potion[potion_contents=\{custom_effects:[{id:"minecraft:speed",amplifier:1,duration:1200,ambient:1b}]}] 1

   to give yourself a potion that inflicts ambient speed II

2. drink the potion
3. drink a regular potion of swiftness
4. the speed II effect will no longer be ambient