I've tested a few z-moves to see if all of their effects have been added and for the most part thats correct. here are 3 that have bugs

1. z-Conversion doesn't give the omni boost it's supposed to. in fact it doesnt give any boost but the conversion part of the move (changing type) still works fine

2. z-Happy Hour does give the omni boost so that isn't the problem. every time i get my gyarados to use it he vanishes in battle (only move ive used that does that.

3. z-mirror move does give the attack boost that its meant to but the mirror move part doesnt always work
I tested it on sludgewave which did damage, shadowball (which didnt affect the mirror move user) which did nothing and psychic which did no damage but lowered the psychic users sp def. i have no idea what causes some to work and some not to

Thanks for the report. However, all of these are known issues that have been reported before. You can follow their status with the below tickets.

Conversion - https://pixelmonmod.com/tracker.php?p=2&t=13357

Happy Hour - https://pixelmonmod.com/tracker.php?p=2&t=13436

Mirror Move - https://pixelmonmod.com/tracker.php?p=2&t=13396