I have been feeding a variety of snakes on aspen from BP to Hognose to KSB without any issue if that put you at ease and not just one or two.
One other thing I would do is downsize the enclosure 20 gallons even for an adult male is BIG but for a yearling 5 gallons, 6 quarts tubs, or V18 tubs would be a lot better.
Temperature wise 95 would be pushing it, 92 at the most would be a lot better with temps in the low 80's on the cool side.
If after that it still does not work try switching from Aspen to coco husk type bedding (needs to be dry of course)