The bug

When you have selected a primary and a secondary effect (that is not regeneration), you can keep that effect even after you switch the primary effect. This allows a beacon to provide two different primary effects.

How to reproduce

1. Activate a beacon with a complete pyramid.

   /fill ~-4 ~-1 ~-4 ~4 ~-4 ~4 minecraft:iron_block
   /setblock ~ ~ ~ minecraft:beacon

2. Select Speed as the primary effect and Speed 2 as the secondary effect
3. Change the primary effect to Resistance without changing the secondary effect
4. Wait for the Speed 2 effect to run out
   Notice that you have both Speed and Resistance. Note that the beacon interface shows that the secondary effect is deactivated.

Expected behavior

Either the beacon interface should shows that Speed 1 is active as secondary effect, OR the secondary (speed) effect should be removed when setting a different primary effect.