Looking for suggestions on how to fix an ABS issue. Two warning lights have appeared permanently on the dash. The amber brake light and amber skid light. I’m not very mechanical. The van rear brakes seemed to stick on one. Very cold mornings and since then the lights came on but disappeared after 30 seconds ish. I also noticed a bit of wheel spin when pulling away. It’s been in to a local garage with a VW knowledgeable mechanic. He was only getting a 10v reading at the wheels. The rear right wouldn’t spin using his plug in machine, but the left one did. He sent the ABS pump away to a refurb specialist who said they couldn’t find a fault. The ABS sensors have been changed but the fault remains. Any pointers would be helpful. I’ve already spent £500 with nothing fixed. Thanks in advance.