JAG Wuppermann

Owner of Hisun Ev1 for 12 months, located in Australia. We use the buggy for collecting on farm firewood and distributing feed to our goat herd. Average <10km per day. Followed all the recommended protocols re charging etc from when we received the buggy in June 2022. Started seeing the dreaded 45C3 warning around Christmas 2022, once or twice but as it was never constant, looked it up in the manual and after a chat with the sparky and no further problems, thought no more of it (getting hold of the dealer was more difficult!). A bit more frequently seeing the 45C3 error by April. Had the sparky out to check the batteries, voltage showing fine. By June the buggy goes 1 kilometre and dies. Finally managed to catch the the dealer, wants photos of low voltage for any warranty claim, and says the only way to see low voltage on a meter is to leave the batteries to drain or not fully charge (or similar). The vehicle won't run long enough before stopping for the batteries to be drained! As in, on for two minutes, off for five, rinse repeat for an hour, and not a single bar disappears on the battery level display. We aren't even covering a kilometre before everything hiccoughs, 45C3 appears and the buggy creeps to a halt. The sparky has been out and completely recycled all batteries twice but that's made no difference (that took the better part of ten days). Had a golf buggy maintenance guy out, he drained the batteries with a neat piece of equipment and low and behold, voltage on all batteries from mid 3s to mid 4s. Reading in forums seems that people have replaced batteries (even after receiving warranty replacements from HiSun, where they were able to get them). Before going the replacement route, is there any other possible cause? This is such a disappointment, and clearly the dealer knows there is an issue (asked how the range had been on the installed batteries and had we considered Li-On, which seems to be discussed a lot on threads once the 45C3 error occurs (!!)). We are fully off-grid, going back to having to drive the diesel utility (heavier on the ground, less manoeuvrability, not to much fuel type and price) is really frustrating. Any suggestions gratefully received please. Thanks in advance.