PHE copper connection replacement

Is it possible to replace the copper elbow that connects to the PHE? The flange behind the nut is so thin I'm struggling on making a tight seal. It's the top near elbow with the sensor. Any advice would be greatly appreciated

Not really unless you have room to cut and fit 3/4 connector.

You could try;
New PHE washer and use grease or silicone grease on the washer. This stops it from twisting round when tightening up. Washer sometimes twists & fold over.

Fernox LS1 leak seal around £5 per tube. Put inside the nut back of & thread. Apply to both sides of washer and PHE connection.
Connect & wait for 30 mins at least.

Tru blu from toolstation is very good small tube about £2 Apply same as for LS1,

Make sure surfaces are clean.
AND there is no part of the old washer behind the nut. If there is you will have trouble.

Use a torch and piece of fuse wire etc to hook and bits out.

Mike
MGC/H2O