Some Inherited Blueprint Variables Breaks After Upgrade to UE 5.5

[brainfart82]

UPDATE

I start getting the feeling that this is a multi-layered issue or it’s really several very similar issues regarding parents/childs/inheriting…

This is a screenshot of our feature testmap playing as a host/server in a shipping build:

The red arrow points at lootable chests that have one(?) of the issues described above. These are child blueprints that inherit the logic and interaction abilities from the parent blueprint but have their own skeletal/static mesh assigned - yet they also show the parent’s dummy geometry.

Clients would also see these chests with the same issue.
However, the only reason why clients can see these chests at all is that we added this to their “begin play”:

So on those childs we created variables with the same meshes as used in the mesh components, and on “begin play” we basically set/assign them once again. Otherwise clients would not see them.

Now adding “-NoZenLoader” to project config → packaging settings had no effect.

However, adding “-NoZenLoader” to the packaged game’s executable (launch options in steam in my case), fixed the chests to not show the white unreal sphere anymore.

Unfortunately, from my understanding that means that the “-NoZenLoader” option fixes the parent blueprint meshes from being shown if the parent had something assigned… but it does not fix showing what the child blueprints have assigned. Let me explain:
In the feature testmap screenshot above, clients would not see any of those dropitems/pickups like trinkets, potions, weapons, armor… because none of them have the soft reference fix on begin play added to them, i only added that to the chests.
It seems to me that the -NoZenLoader option only fixes the parent blueprint stuff from being shown but it does not fix showing the assigned child blueprints stuff.
As mentioned above, we confirmed the issue happening for static & skeletal mesh as well as geometry collection components on child blueprints.

Now, I don’t want to make everyone nervous, but scrolling through various Discord servers that I’m on, I found myself complaining about similar issues being introduced with UE 5.4.4… not sure anymore if we found a workaround back then or if we simply ignored the issue until now that we want to release a demo and do more sophisticated testing, but in case you are investigating, the mentioning of this may having started with the 5.4.4 update might be helpful.

[wilberolive]

I think I might be running into a related issue. When I try to upgrade a project from 5.4 to 5.5 a number of the blueprints break and no longer compile. The issue is that any variables set to an actor base class type have been changed to some sort of PLACEHOLDER variable type.

For example, I have a class called BP_BaseUnit and then child classes of this. Some blueprints have variables set to BaseUnit as the type so it can work with any of the child classes. After upgrading to 5.5 I notice that the types of these variables has changed to:

PLACEHOLDER-CLASS BP Base Unit C 0

[Angius]

@brainfart82

Hey there, the link you provided leads to a 404 page.

https://www.unrealengine.com/en-US/ue-on-github

[Origins (Ganesh)]

Any solution found. My project too broken

[JanHxH_de]

This helped us with our issue with Fatal errors occuring at startup for a packaged shipping build.

Setting to use “IO Store” in the Package Settings/Packaging helped as well but we are going with patching our engine source. That worked as well.

[Major_A398]

I just created a parent weapon where it has a couple of variables, then created a child off of that and it is not showing the variables in the child in unreal engine 5.5.1:

[Major_A398]

Looks like they changed how child blueprints work found it, you have to click on the component then look at details at the top under default: