To replicate issue:
1. Set up scoreboard to count AECs:
/scoreboard objectives add AECs dummy
/scoreboard objectives setdisplay sidebar AECs

2. Summon AECs every tick (active repeating command block):
/execute as @e[type=!minecraft:area_effect_cloud,distance=..50] run summon minecraft:area_effect_cloud ~ ~1 ~

{Age:0, Duration:2, WaitTime:0, Radius:0f}

(This collects all AECs from the executors at the command block)

3. Keep track of AEC count (active repeating command block):
/execute store result score @p AECs if entity @e[type=minecraft:area_effect_cloud,distance:..50]

4. Leave the area (i.e executing entities and command block, if mobspawning is set to false your own body will do the job aswell) (10-20 blocks should be enough, you will see the AECs skyrocket up)

This will show you the overall AECs at the sidebar (skyrocketing and being flushed),
For some reason, the command block/ executing function (which executes at spawn)/executing entity summons many AECs at once if the player is not near the position where it executes.

The 2 pictures show me and an armor stand being the only 2 executors, and when i fly away, the AECs dont stay at 2 (as they should) but increased to 10 (and actually even 20, but i didnt get to screenshot it)