600dpi and above "Failed to Scan: Unable to start scan" on two different scanners
Scans fine at 300dpi or below, but fails at 600dpi or above with dialogue: "Failed to Scan: Unable to start scan".
Exactly the same on two completely different scanners: Brother MFC-L3770CDW HP OfficeJet 5220
Intriguingly the scan does appear to start as I can hear the scanner head move. Scanning colour, over wifi - haven't tried usb.
No useful messages in stdout or stderr or syslog.
Version: 3.36.3 Ubuntu 20.04.1, Intel Core i7-8565U CPU, 16GB Ram