I just got the following error in our Angular build:
ERROR in node_modules/@microsoft/microsoft-graph-types-beta/microsoft-graph.d.ts(20158,15): error TS2304: Cannot find name 'Decimal'.

I believe the issue is located here: https://github.com/microsoftgraph/msgraph-typescript-typings/blob/beta/microsoft-graph.d.ts#L20158

Seems like it was added by this commit: 1b4b132