XF 1.5 Error on Conversation Incoming / Outgoing

[Jayson]

When a community member attempts to start a conversation with me, I start a conversation, or I try and make a reply to an existing conversation, I'd receive the following error:

Please correct the following errors:
The requested user could not be found.
Please enter a valid password.
Please enter a valid email.
Please enter a valid name.
Please enter a value for the required field 'user_group_id'.

The issue only occurs when somebody does something related to conversations only related to my account, it does not impact anybody else. Not the most important issue ever, but it is a problem when users need to contact me.

No error is logged with and without debug mode enabled. This was first noticed after issuing a warning, however the root cause is unknown.

One of the obvious add-ons installed that modify conversations is Conversation Improvements, however I've already tried disabling it and no change was made.

Xenforo Version: 1.5.14

 

[Mike]

It sounds like you somehow have an invalid account, where you're missing data you shouldn't be -- which we've only seen from add-ons.

To confirm though, can you edit your account via the control panel? Can you set things like a signature or your privacy values in the admin control panel or the front-end?

 

[Jayson]

Yes @Mike, I am indeed able to edit values such as my signature, privacy values, and preferences through both the forum itself and the admin control panel.

This issue only occurs in conversations-it use to work flawlessly, though I'm not completely sure what caused the issue.

 

[Mike]

In that case, I might have to recommend disabling all add-ons, not just ones that you think might be related. This can very often be triggered in unexpected ways.

 

[Verringer]

Old thread but in case anyone else has this issue, may as well leave this to help them out.

I found the culprit of this to be ThemeHouse's Sub Accounts addon and a deleted sub-account user still being tied to the user that's receiving/sending the conversation.