Peter, I have used one ASIO driver for all my audio application for a long time without any problems. I have in the past used Reaper, YouTube, iTunes and BIAB, all at the same time with no problems.

Asio4all was installed many years ago and haven't bothered to uninstall it because up to now hasn't given me problem but tomorrow I will remove it as is not longer used.

After doing that, I will reboot the system, start BIAB and change the driver to WAS, then close BIAB and restart the computer and report back.