Did you try and get him from a different angle than usual? Is he nearing a shed? What bulbs are you using in that fixture? What are you using for bedding? Young dragons do best on carpet, tile, non adhesive shelf liner, and a few other solid substrates. Older dragons, since they're less at risk, can be housed on sand but is generally still advised against since an adult dragon can also be impacted if he or she ingest a lot of sand. If your dragon is on walnut shells or sand, it'd be best to use some of the substrates listed earlier.