May be take it back to your shop where it was purchased and tell them what it is doing and let them look at it. I have learned through experience on the job, plus our children have computer (electronic) degrees & builds their own computers from components. Junior high students had me learning in the high speed lane to attempt to keep up with their knowledge. Our son learned how to read and run up his favorite programs on our home computer before he started school. Or maybe your server has a problem similar to our: nemr has grown in customers beyond their band width. It is like a 5 inch pipe drain going down through a two inch pipe connector.
It should not stall on you when your messages are larger (using more memory to react).