If you get an effect with /effect but already have that effect at that strength and higher time, it shouldn't change your effect. But when you do that without particles (/effect @p speed 10 0 true when you have more than 10 s of speed I) it removes the particles from the effect.
Linked issues
Comments 5
Thank you for your report!
We're forward-resolving this ticket as a Duplicate of MC-125785, as the latter contains clear reproduction steps and explains in a bit more detail.
Thanks again!
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The enviroment is only supposed to contain pc details.