i apologize for the barrage of questions that you can't answer. any more info can help others help you and the owner/snake better.
is it possible to ask the owner to post here with more details?
a firm bump is alarming.
i'm wondering if a prey item has rotted in the stomach and caused a massive infection. this would be due to inadequate heat for digestion. this is why we need as much info as possible, as i can only speculate. i have 0 experience with this stuff and am just guessing.
i'm wondering aloud. again, i apologize for throwing a bunch of text at you; i just want to help.