Hi , as I said 2 days ago I also get these errors out of one of my function libraries and I can confirm I use a pass by reference function in there, intentionally. I have one function named “SetAllItemsInArray” and of course this function needs to get the array as reference.
Will you upload a screenshot of your function library so I can have a look ? Additionally , Can you send me a copy of your function library or project? If the PBR is getting reset and I can reproduce that on my end we might have a starting point for why this error is occurring. I believe the error is occurring because that node is switching to PBR, and the reference is returning to the cast node as opposed to any node that would find value with the information, which is why it works when you have a normal input. I’m going to see if I can get the switch to occur on my end or if I can get a REINST error with a PBR on my end.
A screenshot of all functions inside of the function library or only the function with the Pass by Reference Input?
That screenshot was what I needed. I believe the error is being caused in both cases by the same thing. After closing and re-opening the editor, I noticed that the Item pin on the Set Array Elem and the input element pin on the Add Array nodes are setting themselves to a pass by reference that should not technically be pass by reference. In both cases they are attempting to pass back information that has nowhere to go, which is likely the cause of the REINST error. I have entered a bug report, UE-12378 to be assessed by the development staff for this.
Thank you.
Should I still upload my project or are you able to reproduce it yourself?
I was able to repro this on my end so the project upload is no longer necessary.
I wanted to add a comment here that I am also seeing this issue (in 4.7.3), but possibly for a different reason. I definitely don’t have any pass-by-reference in my function library. However, I did use a cast node. The execution pin for a successful cast was tied directly to the function’s return node, and the pin for a failed cast went to a print node so I could print a debug statement. The output of the print node was not connected to anything BUT, when I connected it to the return node as well, the issue disappeared.
Could this be related?
I believe this is a separate error not quite related to the one posted here. Can you make a new answerhub post in the bug reports section detailing what is occurring? If possible, please provide what steps you are taking that reproduce this error.
I think now I was mistaken. Connecting the nodes as I described does not resolve the issue, and I continue to see the Transient.REINST error message (which disappear upon recompiling the function library).
, you should accept this answer, not the other answer above 
Thank you John, I clicked the wrong answer and didn’t even notice!
Just a quick question, would it be possible that this will be fixed in 4.7.5 or will we definitely have to wait for 4.8?
At present this bug is still under assessment. Unfortunately I do not have a timeframe of when it will be fixed, however it is marked as a high priority bug.
Same problem here (4.7.5). Function libs keeps trashing itself after a while.
Do you have an update, is it fixed in the master branch?
This is no longer occurring as of 4.8. There wasn’t a specific commit that I can look up as it seems that a fix in some other bug report is what fixed this error as well. I’m not certain if it is in master yet but it is on the way and fixed in our internal builds.
