Hi Francesco Bucciantini, thank you for your feedback. We did not experienced any similar issue with networking during or after update from previous versions despite we do such a test. As you resolved the problem by reinstall the program, there will not be any information left (in logs) that would help us debugging it. Could you please next time enable debug logging (in Settings → Maintenance - Enable debug logging), try to induce the issue again and send the logs (%ProgramData%\Avast Software\Avast\log and %ProgramData%\AVAST Software\Persistent Data\Avast\Logs) to us (e.g. to ftp.avast.com).

Regarding to your question whether Avast checks the downloaded material for integrity - yes, it does, so if the file is “corrupted” it will not be used.