Just wondering if anyone ever got to the bottom of this one. I haven't even got an L322 but wonder what the problem was. Sad, I know.
No doubt this isn't the fix but once on my ancient Wolseley 4/44 then again more recently on my Triumph Bonneville I had exactly the same issue and it was caused by a blockage in the small hole / port in the master cylinder that allows fluid to flow back into the reservoir when the pedal is released. In both cases slackening a bleed nipple to release the pressure provided a temporary fix until the fluid heated up again and until I cleared the blockage.
Life was so much simpler then.

Hi, I have the same issue after replacing part of front RHS metal brake pipe on moving forward after a short distance it starts to lock up but only on front right as I can feel the heat on that disc. Calliper, slide, etc all good. I’ve come to the conclusion it’s to do with brakes not been properly bled however all seemed to bleed as expected When following the normal process using a self bleed kit.

It’s a 2004 L322

Don't trust what the main dealer says, they know next to bugger all about 2004 models! When we first got our 2005 model we got completely rinsed by 'RR specialist" from then on relied on a good diagnostics unit, Foxwell Nt 530, but there are plenty of other ones available. There should have been error codes showing up, it seems the main dealer didn't give a monkeys or know one. If the brakes have been bled properly you still have to tell the sensors it has been done, sometimes more than once or twice before the failsafe stops kicking in. Suggest you get a good reader or at least borrow one, take a deep breath and then go through the whole process of resetting the sensors, it that fails empty all the fluid and replace it, then start again get a pal to help to make sure you don't get any air in the system because that can play havoc with early L322's. Hope this helps