I see in the topic views there seems to be quite a few people still having this or a similar problem, here’s how I fixed mine.
I had the same issue; it was caused by a third-party node—in my case the “Set DLSS-FG Mode” node from the DLSS4 Plugin.
It broke everything after copy-pasting a bunch of events from my level blueprint graph to player controller graph, including that node. In my case removing said node fixes the issue, but sadly (at least in my case) will leave your project somehow corrupted to a point where you won’t be able to use the broken node inside any graph without it also breaking this graph.
Eventually, I narrowed the “corruption” down to my Custom Game Instance. Deleting a specific unused variable inside my Game Instance, fixed the node.
This variable had absolutely nothing to do with the node, on top of being unused anyway—so there doesn’t seem to be a clear pattern to follow for a fix.
My only advice is try switching to the default Game Instance and see if it works again.
If it didn’t fix it for you, I used the Binary Elimination method to find the origin of the issue, on a backup version of the project.