Please provide more detail. You've removed the actual failing query from the error message you posted, which is the most critical part of it for debugging. I cannot reproduce it; possibly I can with deep code analysis, but that is time consuming.

Sorry, it was pretty long. I've uploaded the page here:
https://bosslife.org/errors/error.htm

Thanks. This looks like a bug after Comcode field precalculation is cleared. I'll try and get a fix out to you tomorrow.

Fixed in https://github.com/ocproducts/composr/commit/b5e01e52cc5e930eddec83bc7885c9f35ad8d57d

This is a class of bug that happens when the Comcode cache ("Comcode field precalculations" OTTOMH) is cleared. Composr has to update the parsed Comcode back into the database when it is missing, but if we have JOINed tables in the data row it tries to save alien data back into the row; we have to pre-filter out what is in the row. Usually we do it right, but there are 100s of cases in the code for us to get it wrong. I think I remember you having a similar issue before.

PHP NOTICE [8] Undefined index: in sources/database.php on line 83 (version: 10.0.15, PHP version: 5.6.30, URL: /tickets/ticket/2_5ae83ddc6693e.htm)

Stack:
https://bosslife.org/errors/newerror.htm

Ergh, sorry, yes. I accidentally triggered an undo in my editor before committing.
Fixed in https://github.com/ocproducts/composr/commit/2296fb769c01366b198c3a69eec3759266e08ac5