It’s a known issue that has now been going on for almost 2 years with various IKEA devices when connected to hubs other than their own. It has nothing to do with smartthings, people report the same problem on hubs of other brands. But not all people, not all devices, and not even necessarily all the time.
The best hypothesis I’ve seen is that there is a routing issue with these devices where when they go through a slightly incompatible repeater they end up doing Long polling instead of short polling, which then uses up battery life like crazy.
If that’s what it is, then the problem could be triggered by a specific repeater, which is why you might have two different devices even connected to the same hub and one shows the problem and one doesn’t.
It’s incredibly annoying, but it’s been going on for long enough that it doesn’t feel like anybody’s going to come up with a real solution soon except to keep trying different combinations of devices.
Ultimately, the solution may be to use the IKEA battery powered devices with their own hub and bring that hub in through matter, but that’s probably a year off at least.
There are several existing threads in the forum already on this, I’m surprised you didn’t find any of those, but in any case that’s what’s probably happening.
Some people have said that one DTH was better than another or one edge driver was better than another, but my own guess is that they just ended up in a slightly different routing pattern the second time and that was what was relevant, not the driver being used. 