This is a weird bug in 5.8.1 with custom Control Rig Modules. I had it in my project and tried to reproduce, but I could not identify exactly what caused it.
The problem is that when adding modules in modular control rig, I can not change values for module variables - as soon as I close and reload the Unreal Editor, values snap back to default values.
I created new module and modular rig and by default it seemed to be working fine. Then I copied over some variables from my own module, added some nodes and the bug started happening also in the new test modular rig. I removed everything I did trying to find the culprit, but the modular rig stayed broken even with just single float variable. I
If I create new modular rig and add the test module - it works. It seems like something gets broken in the modular rig asset itself and stays like that.
In 5.7 it worked fine.
ps: There is another bug that started happening in 5.8, but I think it deserves separate bugreport - it is related to initial transform caching or something. In certain situations i need to change hierarchy (reparent) during construction and change the initial transform of a null. No matter what I do, it will snap the initial value back to what it was before reparenting or during initial creation. It happens only when I move my actor around in scene, but not when I reset it to 0,0,0 - so it seems like some caching issue that happens only sometimes. I will try to make a proper repro - it is quite specific case, but it completely breaks my modular car rigs in 5.8 which worked fine before.
Open CR_ModuleBug modular control rig. Select the CRM_TestModule and change the value of “Variable” from 100 to 200. Compile, save and close the Unreal Editor.
Reopen the UE editor with the project, load CR_ModuleBug and click on the CRM_TestModule - value is back to default 100.
Create new modular rig and add CRM_TestModule to it - change the variable and restart the editor. It should work properly!
This seems to be some specific state of the CR_ModuleBug asset as I could not reproduce it by creating new modular rig or module from scratch. It got broken only after some things I did and removed. My own project is broken completely - all my modular rigs act like that now. In 5.7 it worked fine.
We have come across this internally; tomorrow I will have a public issue that you can follow. This is a regression from a fundamental change in how Control Rig stores variables, which does not play well with modular rigs.
There is a console variable you can add to your DefaultEngine.ini that will restore the old behaviour for newly created assets, but if you’ve created new assets or saved old assets in 5.8, you won’t be able to restore them to the original behaviour.