T1: unknown packet.
175 = the number of the unknown packet
5 = the size of that packet
53 (second) = the number of the packet sent before the unknown packet
53 (second) = the number of the packet sent before the above packet.
Packet 53 is the "send update items" packet you use to send items to an interface (like an inventory, bank or shop).
So either you're sending a packet which your client doesn't recognise or something is wrong with your send update items packet.
My guess is the latter. I would guess you're sending too much data with your packet 53. The overflow is then interpreted as part of another packet.
Check your methods which send the packet 53 and you'll most likely find there's a problem over there.