I understand your feeding live to get started because Silke had been feeding live. It's just that sometimes the feeding itself seems to cause the regurge, but it sounds as if that's not the case here. It could be a case of feeding before the snake is settled in, but usually that will result in refusal rather than regurge.

The big problems I see with this setup are
1) Only one hide (though it sounds like a perfectly good one) = no way to thermoregulate and feel secure/safe. You can buy a piece or two of pvc pipe, ell, or join, or a coconut fiber hanging basket liner, or a clay pot, or a wooden salad bowl, or make a hide from clay or stone or what have you, and have at least one more hide on the opposite side for thermoregulation to facilitate digestion.

2) You don't know the actual surface temps in the enclosure and aren't going to know as long as that's the kind of equipment you have and the way it's set up. The snake spends most of its time on top of the substrate and that's where your measurements need to be taken.

Fortunately, both of those problems are very easy to fix, and pretty inexpensive to boot.