Lots of rims made in china/thailand etc have this problem, Jayco and other vans have had this leak problem over the years, I replaced mine on the Tardis with some good old RoH aussie made jobs which had a decent LR as well, something often overlooked not too bad on dual axle jobs but on a single axle you really need ones specced for 1.2t or more, nowadays I'd go for rims that are mine rated which usually means the chinky rubbish is missing from the catalogue... my 14.44 had 900kg rated rims and the tyres were about the same, totally inadequate for a van at near 1800kgs...............
Since most van wheels/tyres are abused or forgotten about you want quality rims and tyres, I have always gone for a known brand for my vans, they sit around a lot, get screwed around when used and often don't get rotated at age/distance and very rarely get turned when parked up for months on end, so you want a well made tyre thats going to last the years as age is the change over time not distance on van tyres..... Big Mal has Yokahama Geolanders fitted and getting close to 5 years old, at least they have done the miles so be ready in 2 years to get changed, the spare which is one of the old runners will get replaced by one of these yokies................ next year start looking at the get 4 pay for 3 specials, 265 75R16's aren't cheap rubber in LT.....
Triangle tyres have been around a long time along with Double Coin and numerous other brands all made in China, I always reckon suitable for the old work ute but not for something thats is clocking up miles or speed, old boss fitted some double coin to my truck once, he soon realized no savings to be made as blokes wouldn't drive the vehicles or always calling out the tyre mob, mine thankfully found some stakes in a paddock so back to the Dunlops or Bridgies ..................