The most common cause is from a custom field title being too long. The limit is 64 characters however there's are exceptions.
If too much data is sent down to the workstation, this could cause the same response. For example, the length of the message that gets sent from our service back to the workstations must be less than about 3k (it’s a micros limit). So, if you had 10000 offers at 3 characters, that would blow it up as well, and you would likely see the same type of string overflow error.