If there is a spell that summons ghosts for a few seconds to attack, there MIGHT be some problems.

First of all, this is weird to me because a similar function was attempted with cloaked wraiths and the wraiths attacked a nearby enemy without hesitation.

However, in an instance where 9 cloaked ghosts are summoned, what would cause them to not attack? Do ghosts have a passive nature about them? I noticed that when the ghosts were summoned uncloaked, they attacked normally. Do ghosts hesitate to attack while cloaked? Or might this occurrence have been a fluke?

I really want the summoned ghosts to be cloaked because it adds to the dramatic effect... But if there is some unseen force that messes with the ghosts while cloaked and sometimes prevents them from attacking- What is it?

The unseen force is Blizzard Entertainment and its awesome unit AIs. There's not much you can do about it.

However if you let ghosts attack while uncloaked and then attack them they cloak and continue their attack.
Maybe they even continue to attack after being teleported (you need to test that), so you could create them in a temporary area and move the ghost you made aggressive when you need them.

if you hold position with a cloaked ghost last time i checked atleast by hand it attacks things that go around it, you could always run orders after spawning the unit not sure if attack/patrol work, honestly havent tried in forever if ever.

On a related topic of unit AI for attacking, in my arena im making i originally used attack orders which worked good, but i learned patrol worked faster, so i put it in and low and behold my DTs attacked almost instanteously after spawning, but the exact opposite effect for my wraiths and battlecruisers, which spawned and didnt attack. Even with an increased time by 10-15% they still didn't attack in the time it took them to do it with the attack order. Any help is much appreciated as my wraiths with current lifespans of about 850milliseconds with hypers and no wait blocks as to how i arranged my triggers rather smoothly attack around 3-4/5 hits on average spawning 1 by one above a moving target, the BC seems to attack all times now but its killing me for it to have to stay for 1600milliseconds as the effect of attacks with big bulky ships isnt very appealing.

It's not a fluke. It makes sense in melee games when you don't want your ghost to alert the enemy to your nuke attempts.

Cloaked cloakable units such as the Wraith and Ghost will not attack units unless nearby units are under fire.