Import Transactions - DevTools failed to load SourceMap

Trying to import transaction XLSX file got error message: UNDEFINED INDEX TRANSACTION
and this warning on console:

evTools failed to load SourceMap: Could not parse content for https://xxxxxxx.com/akaunting/public/vendor/bootstrap/dist/js/bootstrap.bundle.min.js.map: Unexpected token < in JSON at position 0

Any ideas of why, how, and how to solve it in order to be able to import data?
thanks