Whilst I’m sure TTI and Browan would declare as ‘no user serviceable parts inside’, given its out of warranty by now a competant/qualified electronics eng should be able to diagnose and replace the internal PSU module - its a long time since I looked inside and no time to search forum (try that) where I have seen pictures and call out in the past but you could source a replacement. I think its a stock PSU module from the likes of MeanWell or one of the other well known brands.
Update: I check old photos from when I had a 915Mhz vs 868Mhz misship and looks like it is the Meanwell IRM-10-15. These are stocked by the likes of RS Components, Digi-Key, Arrow, Farnell etc.
