We were facing one issue recently on creating Quote, where in we were getting exception on our Plugin that was registered in Post Update of Quote Detail.
It was kind of surprise for us that why it was getting triggered.
We removed all our others plugin and workflow on Quote and Quote Line but still that plugin was getting triggered. So we thought of trying it out on Vanilla instance of CRM 2016. In case of CRM 2016 the plugin registered on Post Update of Quote Detail didn’t trigger.
We then tried it on Vanilla instance of CRM 2015 On Premise (no online available), and we saw the same case i.e. Plugin getting triggered.
We were getting the following detail on Context.ParentContext (in case where Plugin on Update of Post Quote Detail is asynchronous)
Message – Update
Stage – 30
EntityReference (Target) – Quote
For Synchronous the message will be Retrieve
Hope it helps..