Got a similar situation, on Educated mode. No key or nothing drops after finishing a wave:
The error:
Source map error: Error: URL constructor: is not a valid URL.
Stack in the worker:resolveSourceMapURL@resource://devtools/client/shared/source-map-loader/utils/fetchSourceMap.js:56:22
getOriginalURLs@resource://devtools/client/shared/source-map-loader/source-map.js:75:24
workerHandler/</<@resource://devtools/client/shared/worker-utils.js:115:52
workerHandler/<@resource://devtools/client/shared/worker-utils.js:113:13
Resource URL: wasm:https://html-classic.itch.zone/html/15050453/minipharma.js
Source Map URL: null