Hi Sarah

First thing to ask, where the user ID is being shown, does the user account still exist? This primarily is caused by a user account being deleted. 

Otherwise have you tried a Metadata refresh? 

I would ask them if it is the same user that experiences this? What is their language preference set to? Make sure everyone is set correctly and the correct translations are set. Also do a metadata refresh.

Hi

I did run a metadata refresh and have checked everyone's language and they are all set to the same.  I have just looked through the list and all seems OK today so will ask them to monitor and to screenshot when it next happens.  Thank you

Thank you Matthew, I did run one when on site but it was still doing the same thing.  I will get them to screenshot the next time it happens to see if I can see any pattern in what is happening.  One of the columns was Opportunity Stage too where the code IC was showing instead of the word Speculative but not consistently.  These are the hardest ones to get to the bottom of aren't they.