The SOTAMAS90 DSN is ok but can't handle anything complex. Best thing to do link the tables in Access or use Pass Through Queries and then base your Excel files on the Access database.

MRP is old framework.  I haven't worked with that module before but had to do some work-around processes for custom reports based on WO tables (which is / was also old framework) because old framework files are a less-than-optimal design. 

BigLouie's MS Access / PTQ suggestion is good... personally I prefer setting up mirror tables in SQL Express using linked tables, but whatever works for you.

With PowerQuery in Excel and the issues with the providex odbc driver not being able to efficiently handle large tables when more than one table is involved, i find it best to only query a single table into a worksheet, repeat as need for each table you need so they are each on their own sheet.  Limit columns and apply filters if applicable to limit amount of data returned to excel.  If complex filters are required or you need to wait until another point, that is fine.  Just make sure you only query one table per sheet.  Then you can use PowerQuery to merge the returned data and apply grouping, sorting, filters, aggregates, left/right joins, etc all through PowerQuery.

Another issue you might be encountering is that a lot of those legacy files can be locked by certain sage 100 tasks so you might need to narrow down which task might be causing it by looking at Master Console when the error occurs.

Thanks everyone for your replies. I intend to act on your advice. For now, I'm happy to report that, though the errors still occurred just before running MRP Generation tonight, the ProvideX ODBC driver internal errors disappeared when refreshing the queries right after MRP Generation.