The only amphibian species I've never lost any of them is my FBTs I've had them for years all in goo health, I have had DAFs for about a year I had 5 now I have 4, one got it's foot stuck and drowned..
I've had 4 Axolotl, 1 died of parasites. Had tons of FBNs lost 3 to fungal infection.
I've had half a dozen Tree Frogs only 2 remain, 4 died, they looked like they had a fit, no idea what happened.

I always follow the caresheets but I still loose animals.

I'm happy keeping my FBTs and DAFs for now, would try FBNs again, but I'm realising I'm deffinately a reptile man..