Can someone explain to me what this actually means. I often get rid of it by enavling/disabling or refreshing the solver- but why does it show?
@ssw1 Revit only allows changing the model inside a âTransactionâ. But sometime a transaction results in an error and the error is not handled properly as the transaction needs to be âRolled Backâ to let Revit know it has been cancelled. The message is basically saying that one transaction is already started and you canât start a new one before closing the previous transaction.
As I mentioned this usually happens when there is an error inside a transaction. Do you have any scripted components that might be creating the first transaction?
The only non âout of the boxâ component I am using is the make grid script.
Am I right in saying this issue only occurs when there is a scripted element when transaction start and end are defined?
Yes most probably. It could also be a hidden bug in a OOTB component but that ties to a larger transaction management system so we would have probably had a lot more errors if that was the case. Would it be possible to share your script so I can take a look as well?
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It is the same script as I sent you the other day.
Thankyou!
@ssw1 The GH definition that you sent is very complex and has lots of clusters. I need to be an archeologist to be able to dig deep and try to find the error 
On a first glace around the area that your screenshot is from, I can see at least one component that doesnât handle the transaction errors. If the same scripting pattern has been used in other python components, theyâre going to be a major source of these transaction conflicts.
Follow the pattern described here for a better error handling 
https://www.rhino3d.com/inside/revit/beta/guides/rir-ghpython#handling-transactions
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