Crazy suction line

[Contactor]

Hello

This is a small custom built dairy / drinks fridge running on R404 1.5kg, set point +5c. Superheat fine at about 6 or 7k, low sub-cooling at 2-3k

IE Alco TEV 01 Orifice

LP 4.2 bar / -4c
HP 14 bar / +32c
Ambient +22c

Not perfect, obviously, but working reasonably well.

My problem-

With 7k superheat at 4.2 bar the pipe temperature measured at the phial is about +4c. It's then about a 10 metre pipe run to the condenser in 3/8 insulated tube where it comes off the service valve into a 1/4 suction line to the compressor (it's a small system).

Can anyone explain why the 1/4 suction line from the service valve to the compressor is fluctuating around 0c and freezing up?

Compressor pulling too much vapour through the narrower pipe I guess, maybeit's normal and nothing to worry about?

Thanks