This LDAP might have too many attributes that ends up creating a SQL record that is larger than SQL can handle. Can also occur when the attributes contain binary data that is not handled well. So the way around this is to find out which attributes you actually care about and then we only copy those attributes into the import set. You do this via the Attributes field in the LDAP Server record. You might have to personalize your from to add this field. Once you have the field on the form you would want to populate it with the list of attributes you really need and map in your transform map.
For example:
mail,displayname,company,extensionattribute1,extensionattribute2,extensionattribute3,extensionattribute4,telephonenumber,dn,department,description,employeeid,ipphone,samaccountname,givenname,sn,title,mobile,manager,member
