I am unable to merge two accounts. This is only happening to accounts which were created prior to some date. So problem was probably how it was imported. I noticed all the ones with trouble merging doesnt have anything in created by field. This was because employee who created it no longer works for us and we removed him from the role in CRM. I tried putting the GUID of myself in the account/accountbase tables in the backend database, it does put me as 'created by' but i still get merging error. I dont know if I need to update it somewhere else or if this created By is the actual problem. 

It doesnt give me any specific errors. I looked into SQL profiler and the queries also all seem to point to account table which I did make a change to adding my GUID but it sitll doesnt work. I have attatched the screenshot of the error.
Thanks for your help.