As we are all speculating, from your description of the failure Marmota, my guess is the Centa rollers have failed, although very low mileage for that. The engine was running until you stopped for the picnic, although power delivery problems that you thought were like a drive belt problem. It wouldn't re-start once stopped, although made a lot of noises. The engine is driven by the starter ring through the Centa, no rollers, no engine rotation. Cam belt failure is instantaneous and now very rare since the covers have been vented, particularly at such low mileage. Fuel pump failure would usually give some issues before failure, so it could be the problem. If the battery was dead nothing would be "spinning over like crazy". The ECU usually drops out at about 9 or 10v and the starter solenoid may just about click and rattle at that voltage but not much else. I wouldn't have too much confidence in the standard Banner battery Marmota, it is very marginal. I think the M3W that did the trans India trip had similar symptoms? Interested to see what the garage finds on Monday. I hope I am wrong and it is just a loose spark plug cap.