HP 1920 connecting to HP 1800 and Dell N2048 (Tunk Question)

I hope someone can help,
We have 5 x HP 1820 switches connected via Trunk on each using the SFPs, Recenetly we put a HP 1920 in front of a 1820 due to needing more connectivity, However this 1920 will not connect to our Dell N2048 using dual SFP on a trunk, as soon as its connected (Both SFPs) the network storms and crashes.
I Do have the 1820 sat behind the 1920 using Trunks on Ports 51 and 52 and that does allow communications.
I need ports 49, 50 to be a Tunk to our Dell with VLANs 1, 10, 20, 30 which is currently setup for ports 49 - 52.

Can Anyone help?