The allocation of an extra 2.0 MiB would use more than the limit 250.0 MiB. Currently using 248.0 MiB. dbms.memory.transaction.global_max_size threshold reached
Did the error result from running a cypher statement? Or from clicking the validate button? The error dos not look related to cypher. It looks like something expected a json value but was html instead. If it was related to the validation I would try quiting the browser and return to the class and try again. If it was from executing cypher, please paste the cypher.