2010 V50 1.6D... intermittent electrical fault (?) + stutter

Hey all, hoping someone's been through something similar and can point me in a direction before I start throwing parts at it, bear in mind this is a mystery and I've been posting on different mediums to get an answer.

Yes, Im aware I could take the cr to a car electrician and get it sorted, but I like figuring shit out, you know?

Got a 2010 V50 1.6D DRIVe. Recently had a new starter motor fitted, new battery about 2 months ago (£160), fresh MOT and service. So all the usual suspects for electrical weirdness are either brand new or recently checked.

Here's what's going on...

The main one... heat-related electrical fault

On hot days, or after the car's been sat in the sun for a bit, a cluster of stuff kicks off at the same time after driving for 2 mins:

• "Brake Failure" warning on the dash
• "Anti Skid Service Required" / ABS warning
• Speedo and rev counter go completely dead, needles just drop
• Clutch and throttle feel heavy and weird
• In first gear specifically, the clutch won't bite properly without me flooring it... have to really rev it to pull away. This clunky clutch thing ONLY happens when the warning lights are active, it's totally normal otherwise
• Whole car just feels off when this is happening

It's fully intermittent. Can drive perfectly for days then boom, all of the above at once. Cools down... fine again. Had it into a couple of places when cold and they've all found nothing, which makes sense because the fault isn't there when it's cold and static.

One time it wouldn't even crank. Full dash, complete silence at the starter. Left it a while, temperature dropped, started fine.

Separate thing... small stutter under acceleration

This one's always there, hot or cold. Very subtle little tug/power loss when accelerating. Mainly around 2k rpm, worst in 2nd and 3rd. It's not dramatic, not limp mode, not a cliff-edge, just a tiny hiccup like a signal's cutting for a split second. Car pulls fine otherwise.

And the alarm...

Goes off on its own maybe once a day, random times, car just sat on the drive locked. No pattern I can see.

Background/history that might be relevant:

• EGR valve was crimped and patched with JB Weld Extreme Heat plus a clamp, still holding. The EGR itself is a cheap Chinese aftermarket one though, not OEM
• Had P1577 and P193B accelerator pedal position sensor codes a while back, pedal got swapped for a used unit, drivability fixed but the codes never got properly cleared (generic OBD wouldn't clear them, need Forscan for the APP relearn which I haven't done yet)
• Got 2 keys, one I use daily, other basically never gets used

My hunch

Given everything points at intermittent and heat-sensitive, and battery + starter are both new, I'm leaning toward it being a power distribution or earthing issue rather than a single failed part. Main engine earth strap, battery earth at the chassis, or something in the fusebox/CEM (I know these are a known weak point on V50s, cracked solder joints, water ingress from blocked scuttle drains, corroded pins underneath etc).

Alternator diodes also crossed my mind, could explain the stutter too if voltage is sagging under load.

But I'm not a mechanic and I'm spitballing. Anyone seen this specific combo before? Anywhere obvious you'd check first? Anything I'm missing?

Cheers
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