GrapesJS builds on macOS but not on Windows 10+

I am hitting a wall on this one. I am building GrapesJS, a web page editor (https://github.com/GrapesJS/grapesjs). It builds fine on macOS but not on Windows 10+. Same version of node, latest release of VS Code, same updates and dependancies.

WARNING in ./src/common/index.ts 35:2-16
export 'default' (imported as 'Backbone') was not found in 'backbone' (module has no exports)
 @ ./src/editor/view/EditorView.ts 16:0-39 45:21-22 68:2-6
 @ ./src/editor/index.ts 60:0-43 866:30-40
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/common/index.ts 43:2-21
export 'default' (imported as 'Backbone') was not found in 'backbone' (module has no exports)
 @ ./src/editor/view/EditorView.ts 16:0-39 45:21-22 68:2-6
 @ ./src/editor/index.ts 60:0-43 866:30-40
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/common/index.ts 51:2-15
export 'default' (imported as 'Backbone') was not found in 'backbone' (module has no exports)
 @ ./src/editor/view/EditorView.ts 16:0-39 45:21-22 68:2-6
 @ ./src/editor/index.ts 60:0-43 866:30-40
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/dom_components/model/Component.ts 1597:18-45
export 'Model' (imported as 'Model') was not found in 'backbone' (module has no exports)
 @ ./src/dom_components/index.ts 97:0-74 262:23-32 267:26-35 588:30-39 588:41-56
 @ ./src/editor/model/Editor.ts 91:0-52 138:4-20
 @ ./src/editor/index.ts 59:0-41 79:22-33
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/dom_components/model/Component.ts 1625:25-53
export 'Model' (imported as 'Model') was not found in 'backbone' (module has no exports)
 @ ./src/dom_components/index.ts 97:0-74 262:23-32 267:26-35 588:30-39 588:41-56
 @ ./src/editor/model/Editor.ts 91:0-52 138:4-20
 @ ./src/editor/index.ts 59:0-41 79:22-33
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/editor/model/Editor.ts 113:0-10
export 'default' (imported as 'Backbone') was not found in 'backbone' (module has no exports)
 @ ./src/editor/index.ts 59:0-41 79:22-33
 @ ./src/index.ts 13:0-30 61:25-31

WARNING in ./src/undo_manager/index.ts 76:23-34
export 'default' (imported as 'UndoManager') was not found in 'backbone-undo' (module has no exports)
 @ ./src/editor/model/Editor.ts 108:0-51 118:4-21
 @ ./src/editor/index.ts 59:0-41 79:22-33
 @ ./src/index.ts 13:0-30 61:25-31

All of the config files are the same between the instances. I can browse to the backbone node_module. I have tried various path configs. I have tried both imports * as Backbone from 'backbone' and imports { backbone } from 'backbone' to no avail. Along with various modifications to the webpack.config.js and tsconfig.json. All the usual stuff. Two days of head banging and no love yet.